The transcript below is derived from the VIN/VSPN Rounds presented on November 15, 2020. Click to view the slides.
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Carla Burris: Tonight's speaker is Dr. Scott Weese, from Ontario Veterinary College's Centre for Public Health and Zoonoses. Dr. Weese is a veterinary internal medicine specialist and an expert in infectious and parasitic animal disease. He is invited to speak often on infectious disease topics, and he is currently very busy due to COVID-19. You may know him as a VIN Consultant in the Infectious Disease folder and an author of the Worms & Germs blog.
Welcome, Dr. Weese!
Slide 1 (View the slides.)
Scott Weese: Thanks a lot for having me. Thanks to those that came in on a Sunday night.
Today, I'm not going do the whole COVID spiel. We’re going to focus on how we practice in the COVID era, which is going to go along for months. We don’t know when it’s going to end, but it’s going to be a little while, so thinking about how we get through the next six months or so is still an important thing.
I'll start off with a little bit of basic background, not on the COVID background. Everyone is COVIDed to death.
Just a couple of quick updates – I'm not really going to go over this. We know that most places are in a second wave, although some places really never exited the first wave. Regardless, what’s going on, as you know, is that in many places we have increasing case numbers, increasing hospitalizations, and increasing deaths – which increases the risk of restrictions. That probably ties into two important things for us in clinics. One is the risk, because there is more disease in the community and that’s more risk coming into the clinic. The other is restrictions that might be put in place and how we act, and the things that we need to do to show that we don’t need to be restricted. I think the more we say that we’re good, leave us alone, we’ve got it under control, I think the better for us.
Hospitalizations are going up, and that’s one of the big things. I'm not going to get into data. I was going to talk about how to assess COVID in your area and what the risk might be. I'm happy to chat about that after, but I want to get into the meat of the clinic side first.
Realize that the rates are really variable internationally, so where you are might be quite different. Even within countries, the rates can vary quite a bit. Some places have done an exceptional job of controlling. New Zealand is an obvious example. There are advantages to being on an island. Australia has done a very good job bringing it down. They’ve had great success in bringing cases down without profound long-term restrictions. Some places in central Europe are a disaster right now. Some places in the U.S. are a big mess too. It does vary quite a bit, and I think it shows what happens when we relax too much.
Really quickly on the animal side, what species can this virus infect? I'm not going to go through them all, but I'm going to talk a little bit about a couple of our main species.
You have to be thinking about the risk that the animals might pose to you – animals that have infected people and what they might pose to you (or what they might not).
The good thing for us is that dogs are susceptible, but they’re not highly susceptible. Experimentally, they’re really susceptible. They don’t seem to get sick. It's debatable whether some dogs will get sick. There are a couple of reports of dogs that have been sick, but we don’t really know if that was a dog that had COVID or a dog that had something else and was also coincidentally infected with this virus.
They certainly can be infected. If we look at some early but increasing seroprevalence data, it’s maybe not that uncommon that we see human-to-dog transmission in a household that’s subclinical.
From the little bit of work that’s been done, there is not a ton of virus being produced by these dogs. There has been one case where a virus was isolated from a dog’s nose, so a live virus, and that indicates there might be some risk. Most of the time, though, the viral loads that we’re seeing in dogs seem to be pretty low. What we’re hoping is that they’re predominantly a dead-end host. Yes, we get regular probably human-to-dog transmission in households. Dogs typically don’t get sick, and they probably don’t shed enough virus to pass it on.
When we think about dogs that are coming into the clinic, there is still some risk. We would have to assume a dog coming from a positive household poses some risk. It’s going to pose less risk than cats. The risk probably isn’t great. The risk from the hair coat is probably close to negligible unless the client has just coughed on that animal right before it came in and we touch it and touch our face.
We’ve backed off on some of our concerns, but there still is a theoretical plausible risk working with dogs. Really, we only focus this on dogs from high-risk or known positive households.
If you’re interested in the U.S. data, U.S. data are all put out by the USDA. If you Google USDA and COVID, you should be able to find it.
There are a reasonable number of dogs and cats. It’s not a huge number when you consider the population that’s out there. There’s not a lot of testing that’s been done, though. We just don’t understand the scope of the issue, and since we’re doing more serology, we’re finding it’s probably not that uncommon to see transmission.
Cats are a bit of a different story. We’ve been worried about cats all the way along since this virus emerged. That’s largely been proven true to some degree. Cats are relatively susceptible to the virus, and they can get sick. Most often they don’t, but they can get respiratory disease and it can get GI disease. There are some reports – not many, but some reports – of fatal infections. There is one in pre-print that shows a fairly clear fatal infection in a young cat.
We get the gamut of illnesses ranging from subclinical in probably the vast majority of cases, to mild disease that we maybe don’t hear about. One thing that we find in our surveillance when we’re talking to people, when we’re polling households for active surveillance, they say, “Yeah well, when we were sick, the cat was quiet or didn’t eat as much or it was coughing or sneezing a little bit, but it wasn’t that bad. We didn’t really think it was a big deal until you started talking to us about it.” We don’t know whether that’s the recall issue or whether there really is a high risk of transmission with really mild disease.
One thing about cats compared to dogs is they are more susceptible. Experimentally, we know cats can spread it cat to cat. They’ve got enough virus there to infect another individual. If they can spread it cat to cat, it’s certainly reasonable to think they can spread it cat to person. Is this happening? We have no idea. The problem is that there is so much human-to-human transmission, it’s really hard to identify whether there might be an animal source. If we have COVID in a household, what disease could be attributable to cat versus the person? The person is the more likely source. This is really why we counsel keeping animals of exposed individuals away from others, because we don’t know. For cats, there is certainly some degree of risk. Clinics flagging this risk is important. If we have a cat coming from a known positive household, that’s a higher risk situation for me. The more contact we have with that cat, the higher risk that is if that’s an aerosol-type contact. I'll come to that in a little bit, but certainly cats are susceptible, and cats are the bigger concern.
Then we get into mink. Mink is a really interesting story and I'm not going to get into it too much, but mink kind of caught us by surprise...but kind of didn’t. We were expecting ferrets to be a problem because we know ferrets are susceptible to a lot of our respiratory viruses. They were susceptible to the original SARS. Experimentally they are quite susceptible, but it’s the mink – the close relative to the ferret – that caught us off guard. This happened because of human-to-mink transmission on mink farms. Mink are really susceptible to this virus. It gets in the farms very easily in endemic areas, and it spreads very widely.
This is a quick map I did earlier today of areas that have identified mink. Greece was added to the list. We don’t know about some of the big mink-producing areas. We know Denmark is one of the big producers. They’ve got big problems that I'll get back to in a second. Poland is a massive producer. Russia is a pretty big producer. China is a huge producer of mink and we don’t have information from there – whether it’s not occurring, whether they’re not looking, or whether it’s don’t ask/don’t tell.
We’re a bit concerned about mink because of the stuff you’ve probably heard in the last week or so. I'll only touch on this a little bit because you’re bound to get questions about it. This is concern about a mink strain or mink variance.
Any time a virus moves like with person-to-person, there is some risk of mutation. Viruses mutate all the time, and that can be good and bad for us. It can make them less virulent, more virulent, less transmissible, or more transmissible. It’s random chance.
When they move to another species, we have a greater risk of mutation because they’re trying to adapt to their new host. When they’ve got a lot of individuals to infect, we have a greater chance of mutation because there is more transmission. The more passages, the greater chance of mutation.
You take a virus and put it into a mink farm – so you have jumped species where there are thousands of them – it makes sense. It’s a classic place where we’re going to see some viral change, and that has happened.
Now, this has raised two concerns. One is that mink-to-human transmission has been identified in the Netherlands and it’s now been identified in Denmark. It wasn’t a huge concern because there aren’t that many people that have contact with mink, so mink workers were worried about it, the general population, but not really as much until this report came out. This is talking about different mink variants. Like I said, we expect them to happen, but one mink variant that they’re calling a mink strain now accounts for a large percentage of infections in a region of Denmark where there are a lot of mink farms. What’s happened is this has gone from a person to mink on a farm, it spread on the farm, it’s mutated during that spread, it’s gone back to people, and that strain is now spreading widely in the human population, so it’s still nicely able to infect us.
The concern is that it has mutated enough that it might be different enough to cause problems. We don’t really know yet, but when they look in vitro, antibodies from someone infected with the normal strain of this virus don’t neutralize this variant quite as well as they would a normal one. That raises a bit of concern for antibody-based therapeutics and vaccination. We don’t know if there is enough change for that to be relevant, but it’s a concern considering how widely it spreads. This isn’t being spread mink to human over and over again. It went into the mink, changed in the mink, got kicked back into people, and now it’s a human problem that originated in mink, which originated in people.
It's that general message where we’ve been trying to say, “Let’s keep this thing out of animal populations so stuff like this doesn’t happen.” This is a concern anywhere you have large populations of susceptible animals, and really mink are our main concern because our domestic livestock species don’t seem to be susceptible. So far, our main wildlife species we have looked at don’t seem to be susceptible, so mink are our main concern right now in the semi-domestic or domestic animal mixing vessel. It hasn’t gotten out in the wild mustelids as far as we know, but with mink farms there has been exposure to feral cats. There are a lot of concerns that come up with that, so it’s something we’re going to hear more about certainly.
I'm going to move off the animal side now. If anyone has questions, toss them in the chat and I'll try to keep an eye on that as we go.
If you’re looking for more information, a summary on different animal species, I've been doing a series of reviews of different species. I think I hit #7, which has to do with cattle. These are on our Worms and Germs blog, or you can find them through Twitter (@weese_scott). These are fairly quick synopses of what we know on different animal species, and it’s quite variable from they’re really not concerned at all to yeah, we’ve got something to worry about (not worry but pay attention to).
We talked about transmission before. You’ve heard about this ad nauseam. The transmission story continues to evolve. We learn more about this virus. It’s never been black and white, and that’s been a hard message to get across. We’re understanding a little more of the shades of gray than we did earlier on.
Predominantly, this is droplets and direct transmission, and then you get into aerosols. Aerosols/airborne is where people get a little freaked out and they get a little bit concerned. I'll touch on that in a couple of slides. Then there’s fomites or surfaces, which I'll hit on again later. It’s not really that big a deal. We were a lot more worried about surfaces back in the spring. They are not panning out to be a major concern, so direct contact, droplets, and certain types of aerosol transmission – that’s what we’re worried about, and that’s what we need to think about in terms of our risk of transmission.
One thing that gets talked about a lot is this 2-meter or 6-foot distance. If you stay that far away, the risk is lower. The key is the risk is lower; the risk doesn’t disappear. The virus doesn’t go 6 feet and then boom, it dies. It goes certain distances. More of it settles out, so as I'm talking, and if I'm infected, I’m making some fairly big droplets that don’t go very far. They’ll hit the tabletop in front of me. Some will go a little bit farther. A small number of those will be fairly small, especially if I’m coughing, sneezing, singing, and talking loudly, making these little particles that drift a little bit farther. Those usually aren’t a big deal if they disperse, but if I'm in a small room with no ventilation doing this for a long period of time, that small percentage of small particles suddenly becomes a bigger, bigger, bigger number. They form this cloud around me, and that cloud might reach critical mass in terms of infectivity because there’s a dose component here too.
We don’t think of this as...it’s not measles, it’s not airborne, where I'm in here and I'm making this aerosolized, airborne virus and someone walks in this room three hours later and they’re infected – that’s an airborne virus. This is not an airborne virus, but it is an aerosol virus. That’s a message that’s a bit hard to get people to understand, but that really ties into things about mask use. It ties into things about room size and ventilation – the stuff I'm going to focus on a little bit later.
This picture depicts the variance. It’s underneath my chat so I can’t see it really well, but you see we’ve got big particles and we get small particles. We have mainly big particles, but the more small particles we get over time, the greater the risk that they go farther and they accumulate. The risk doesn’t disappear at 6 feet. The risk drops, so there is some risk at 5 feet and some risk at 12 feet. If I'm really sneezing away and I'm really infectious, that risk could go across the room over time if there is poor ventilation, and that’s where we can control time, and we can control ventilation. We can control things that make me aerosolize or the things that will stop me from aerosolizing as effectively.
If you’re going to think about anything COVID controlled, this is the slide to think about. These are the three Cs (or the four Cs, because I added one in there).
The three Cs are closed spaces with poor ventilation, crowded places with people nearby, and close-contact settings. We need to maybe think about them to differentiate them a little bit. If we can think about the three Cs in the context of our clinic and different parts of our clinic and how we can modify them, then we can control this virus. We think about what’s bad for three Cs. Think of an exam room. For me, exam rooms are biohazardous in our normal operation. They are closed spaces, they’re small rooms not always all that well ventilated. They can be crowded places because we have a couple clients, a veterinarian, a technician, and we have a number of people within that small room, and we’re doing things in close contact when we’re talking, and there’s talking loudly. We’re making these aerosols over time, so when we put these three things together, we create risk.
When we want to mitigate that risk, we think about how we withdraw that. Closed spaces with poor ventilation – well, I can’t make my room bigger, but I can improve ventilation. Crowded places with many people nearby – well, I can decrease the number of people that are there or not bring them in. For close-contact settings we can separate, or we can do things that decrease our risk of aerosolization. This might include masking, but there are a whole range of things that we can bring in.
Then there’s that fourth one, which is continuous – so there’s a time component. The more time, the greater the risk. Because I'm producing more virus, I'm creating more risk over time. That transient thing – walking by someone on the street, it’s not a closed space. We’re in a big outdoor area. There is great ventilation. Is it a crowded place? Well, it’s a crowded place for a second as I'm walking by. Is it a close-contact thing? Not really, right? Depending on what we’re doing, but it’s that really transient thing and the continuous aspect isn’t really there. The more we start cramming people into places, the more we start putting them in close contact within those small rooms, and then the more they’re doing things in close contact, the greater the risk that comes up. This is really a key thing in terms of control.
This is another one. This is a really important concept for me when it comes to how we control it and how we change things, because we never do things exactly like we want to do. This is the Swiss cheese approach to disease control. It’s really straightforward, right? We’ve got lots of things that we can do. None of them are perfect. Masks aren’t perfect by any means. Ventilation isn’t perfect by any means. We’ve got no magic bullet, but we’ve got lots of things that we can do to reduce that risk. When we start layering Swiss cheese on, you take those holes away. We’re trying to use multiple things. We can’t just say, “I'm cleaning and disinfecting so I'm good,” or “We’re wearing masks so I'm good.” We’ve got to do multiple things to be effective. If we can’t do one of them, we’ve got to the other things really well.
Let’s say we have really crappy ventilation, so we’ve got a really big hole up here. Well then, we need to do the other things really well. We can back off on something sometimes, because sometimes we have to. There are situations where we have to do the things that are suboptimal, but we have to not just say, “Okay, well shit happens. That’s just the way it has to be.” No. We have to do that, but what else can we do? How can we make sure we’re maximizing the use of these other components of the Swiss cheese so that we’re not substantially increasing our risk? We shouldn’t just say that we can’t do it and move on. If we can’t do it, what else can we do? How do we make sure the other stuff is done right? We can do that without being too disruptive, and that’s really the key – balancing that protection and the practical nature of it.
For vet clinics, we’re limiting access. We have distancing, we have ventilation, we have masks, we have hand hygiene, and we’re keeping people out as much as we can. On the public health side is contact tracing, and then we’ve got surface cleaning and disinfection. By picking and choosing these or using all of them as best we can, some more than others, we can really reduce that risk.
We can combine that with thinking about the three Cs, and we can practice very, very safely with some common sense.
I'm not going to get into politics and masks, because that can be pretty nasty. I'll just say that masks work. Masks are very effective for reducing aerosolization. If I'm infected and I'm wearing a mask, I will drop the number of droplets I release. I will reduce the number of aerosol particles I release. It won’t eliminate them completely. It’s Swiss cheese it’s got holes in it, but I'll drop it.
It will also protect me to some degree. Masks are more to protect from me because they can protect over things making these aerosols. They don’t protect me as much because I'm getting things in my eyes. My eyes aren’t protected. I'm just wearing a mask. If I'm worried about a respiratory virus and I'm wearing PPE, I've got eye protection and a mask. It’s not perfect, but there is some personal protection component of wearing a mask.
That messaging has changed a little bit. Before, it was really being pushed as masks protect others. Now, its masks protect others and, yeah, they’ll help you a little bit too. That might help with compliance too.
When we think about masks...I'm thinking about this in part for medical procedures where we would usually use a mask, like a surgical mask in a surgical procedure. Think about masks for routine use. We’ve got various things we can think about – cloth masks, non-medical single-use masks (although the single-use masks can be re-used within limits), medical masks (normal surgical masks, or procedure masks), and N95 masks.
The bottom two – medical masks and N95 masks – are considered PPE if there is an investigation of exposure. It doesn’t usually change all that much because you’re not protecting your eyes. We won’t say to wear a medical mask over a non-medical mask. If you get exposed to an infected person, they’re not going to say, “You’re good to go if you were wearing your surgical mask. You have to isolate if you’re wearing a cloth mask.” That’s very rarely going to be the case.
When we think about the use in clinics for routine things, it’s cloth masks and non-medical or medical masks.
What’s the difference between those?
Not necessarily much when it comes to medical versus non-medical masks. Cloth masks are quite effective. They are variable in their design. You can’t have as much confidence in them as something like a medical mask, but they are quite good and they are easy to get.
With non-medical versus medical masks, the difference can be really minimal. The medical masks are made to a spec, and there is quality control there, so you know what you’re getting ,or we can assume what we are getting. With non-medical masks, you can’t make that same degree of assumption, although you probably are getting the same thing out of it. Some non-medical masks are medical masks that are branded as non-medical masks because there’s a big market for non-medical masks, because the messaging has been to use non-medical masks. Save medical masks for healthcare. Wear a non-medical mask. If you’re a mask producer, it’s okay. It’s the same stuff, different boxes. This one says medical; this one says non-medical. There’s nothing wrong with that. They're marketing for different groups.
Your medical masks and your non-medical masks may be very similar. You just have more confidence in your medical mask because you know they’ve been designed to a specific standard; the non-medical masks tend to be very good overall.
A number of people have come up to me and said, “Oh yeah, you’re supposed to wear a mask one way or another? I never knew that going into vet school.” Yeah, we’re supposed to wear a mask a certain way. The blue side typically is on the outside.
Really quickly on masks – you’ve got an inner hydrophilic layer (an absorptive layer), you’ve got a middle filter layer, and you have an outer hydrophobic layer. If you reverse it, you’re kind of getting the opposite. You’ve got it absorbing it from the outside and repelling your own secretions back at you on the inside, so you are supposed to wear them one way.
You can reuse non-medical masks. We don’t know how many times. If you take them off, don’t crumple them up, don’t break the seal and don’t get tears in them, you can use them at least quite a few times. You can certainly wear them over the course of the day taking them on and off carefully.
Q: How many uses or how many days does a N95 or KN95 last before it is not useful?
Scott Weese: CDC has changed their messaging a little bit. They have some information – I think five donning and doffings is what they’re saying last. I'll have to check that. The concern is really the damage that happens every time you put it on and off. The more careful you are, the better.
There are very few situations where we’re going to need an N95 in practice, or a KN95. KN95 is the Chinese standard for an N95. They are basically the same thing, but you can reuse them multiple times. We can’t really say an exact number because it comes down to how they’re being used and the degree of contamination they might get. Certainly, you can wear them a number of times. There are various reprocessing things have been looked at to extend that, to kill things on them. They are pretty solid masks. They can handle quite a bit of use.
The other thing that’s come up quite a bit with medical masks is people are actually reading the labels. They never did before, right? I didn’t.
We’ve got Level 1, Level 2, and Level 3 medical masks. We get a lot of questions. “Are Level 1 medical masks fine?” Yeah, they are. Level 1 is mainly what they use. These are the low-barrier masks, the general normal surgical things.
A Level 1 mask basically is there to be able to repel blood that you might get from indirect contamination, so you touch your mask inadvertently and you get blood there, okay, that’s not going to go through. A Level 2 mask will take fluid under pressure, so for an arterial spurt that hits your mask, a Level 2 will protect; a Level 1 may not. Level 3 is just one step up.
We typically use Level 1. Level 1 is fine for an aerosol virus. We’re not looking at things coming at us with force and volume and liquid. Whatever you can get, most of that is Level 1 and that will be fine.
This shows that they're made with slightly different specs in terms of their fluid resistance and how much they filter, but overall they’ll all do what we want them to do, so whatever type of mask you can get.
I’d say in general we’re not having problems sourcing these like we did back in the spring, so there’s a little less concern about re-use and the like, but some people still run into some issues.
A couple of last things about masks. Valves – I think we’re getting this message out pretty well. Valved masks are bad, put it that way. If you see a mask that’s got a little plastic piece on it, that’s probably a valve. It’s a one-way valve. They are sometimes marketed as an easy breathing mask, and they’re easy breathing because they don’t filter anything.
Here is an N95. This is a high filtering. This is a mask we use in higher-level containment. It's got a one-way valve, and that’s fine if you’re using it just to protect yourself. Usually when we’re talking about N95, we aren’t worried about what we’re breathing out – we’re worried about what we’re breathing in. That’s not the situation here.
This is just a little quickie thing I did a while ago. I took a cloth mask, a surgical mask, a regular N95, put it on, put a culture plate in front of my face, and talked and yelled. I did the same thing with a valved mask. You can see the chunks that came out. There were a lot of bacteria versus nothing there.
If you have staff wearing valved masks, that’s easy – just say no. Places are getting pretty good about this. I see a couple of airlines have banned them. Business places are banning them. Don’t let your staff wear these. It just creates an unnecessary risk. There is no reason to have them. You might as well not wear a mask. They give you some protection, but not a whole lot.
With clients, it’s a little bit tougher if they come in with that type of mask. You can try to educate them. I think I'm seeing fewer and fewer of them because the message is getting across, but you still may see them.
I'll skip over that.
When to use different types of masks – this is a table from a document. We released a series of guidelines in Ontario that were taken in different places. You can find them on https://www.wormsandgermsblog.com/ or you can email me. This is very similar. CDC has come out with similar guidance. Basically, cloth masks are fine for routine procedures, and we started getting into increasing risk of this patient being infected. We start getting to a mask we have more confidence in, which is a medical mask. If we start doing procedures where we’ve got a real risk – we think that this animal is infected and infectious, and we’re doing something high risk – that’s when we get an N95.
For me, the N95 is for when you’ve got a cat coming from a positive household. The cat has a fever or it’s got respiratory disease, and for some reason you have to work closely around its face or intubate it. That’s an aerosol-generated procedure. That’s a high-risk patient. I want an N95. I want eye protection. I want gown and gloves.
Otherwise, you don’t really need an N95. For a high-risk species from a high-risk household, if you have N95s and you have enough of them and people know how to wear them when they’re fit tested, there is certainly not a downside to them as long as we have capacity in health care system when they need them – but they really aren’t needed apart from the high-risk things. This is a fairly similar line that’s being taken in people where there was a lot more use of N95s to start, and we’re realizing we can back off that now. Certainly, when I was doing field survey on outside animals, I was garbed up a lot more aggressively at the start, and now we’re realizing the risks are a little different, so N95s you shouldn’t really need much – just good use of regular masks in different situations.
Face shields come up a lot. I think we see a lot fewer face shields now, which is good. Face shields are not a replacement for masks. Face shields are there to protect your eyes, to give you a back-up plan over your respiratory tract. They are not there to prevent things from going in, because they don’t seal right. They are pretty wide.
This visual shows it nicely. Here’s a person on the right wearing a surgical mask. When they breathe or cough, yes, stuff comes out because it’s not meant to seal completely, but not a lot comes out and it doesn’t go straight out at someone. It kind of drifts around the sides and top like you would expect.
With a face shield, you get a whole big plume of this stuff that comes out, then it hits your chest and neck, and then it shoots straight out. Face shields aren’t a replacement for that.
I've heard some people say they’ve seen face shields more at a restaurant. I haven’t been restaurant dining since this all started, but they talked about servers wearing them – which is likely the worst place you can have a face shield. Think about it. You’re sitting at a table, so the server is standing above you. They're breathing, and they’re directing their plume of secretions right on you below them. If they’re infected, they’re just funneling this stuff right on you.
The take-home is you shouldn’t be using face shields as a replacement for a mask.
There is a protection component to this too. There is a...well not nice, but there’s a nice example of a restaurant outbreak in Switzerland where there were a number of people who were infected. It was people who wore face shields for their own protection. The face shields don’t protect from aerosolizing very well, and they don’t protect you. The people with face shields got sick. People with masks didn’t. It’s an N of 1, but it kind of shows that. They're not meant to be used by themselves. They're an adjunct, and they’re largely to protect your eyes.
There’s an exception to every rule, right? There are some situations when you might need to use a face shield, or you might need to use a clear mask.
I've never actually worn one of these. I'm sure how effective they are.
There are some clients that will need to be able to see your face. They might be deaf and they need to lip read. They might be someone that just needs to read facial cues. There are some people like autistic people that certainly need to read facial cues, and you might know that, or they might tell you that. This is where the Swiss cheese approach comes in, as opposed to saying, “I won’t wear a mask.”
I'm going to wear a face shield all the time in case someone needs to see my face? No. I'm going to wear a mask all the time, and if someone needs to see my face, you can put a sign up to let your clients know. However, it’s done, okay, I'm going to use a face shield instead of a mask, and I realize I'm making a big hole in my mask component of the Swiss cheese. What does that mean? Well, that means I need to pay attention to everything else, so I'm going to stay farther back. I'm going to distance as much as I can. I'm going to be in the best ventilated area I can be. Maybe that’s going to be talking to them outside. It’s not going to be stuck in an exam room with the door closed and crappy ventilation.
I’m going to focused on maximizing all those other components, so that while I'm increasing the risk a little bit by wearing a shield, I'm correspondingly decreasing it by doing some other things that I maybe don’t do all the time because they’re more cumbersome, but I want to bring them out here.
I'm not saying don’t ever use face shields, because some clients will need you to use a face shield. We just don’t want to fall down to that, and when we do it, we want to maximize all the other stuff that we’re doing.
For me, the take-home on the face protection mask side is that everyone in the clinic should wear a mask. Full stop. End of the day. That’s it. If you’re in the clinic, you wear a mask.
If people need to be on a phone and they can’t talk comfortably and they want to have a mask off, then we need to figure out how to do it. It’s that Swiss cheese approach. If they want to have a mask off, they need to be distanced, we need ventilation, we need to think about time and all this so that they don’t pose a risk, or have them off-site if they’re just using the phone.
Non-medical masks remain the standard for non-human health care situations. They're for routine use. If we’re using them for a procedure for a high-risk case, that’s different, but if we’re just talking about normal day-to-day use, then a non-medical mask or a cloth mask is fine – and face shields are not.
I mentioned fomites at the start. I was a lot more concerned about hand hygiene and fomites and that stuff when this thing first emerged. I really don’t care that much about it now. It doesn’t mean I ignore it. It doesn’t mean I don’t think cleaning is important. Disinfection is important. Hand hygiene is important. We just don’t have good evidence that the environment is a reasonable source. If I'm infected and I cough in my hand, I touch a doorknob, you come right after me and touch the doorknob and stick your hand to your face, well yeah, there’s a risk there. Right? There certainly is some, but we don’t have great evidence that there is a lot of environment transmission. There is very poor evidence of environmental transmission.
You get the odd news report or paper that comes out. Here’s one that was a couple weeks ago – “Coronavirus can remain infectious on bank notes and other surfaces for weeks.”
The take-home was yeah, in a lab, but not really in the real world. If this was really spread nicely by fomites, we would have a different epidemiology. In places where rates are low and contact tracing is really effective, you would find more unknown cases. If I'm going to the grocery store and I'm touching surfaces, and people are touching in there, I'm going to have a lot of unknown things versus we can link most of our cases. When you’ve got good contact tracing in a low disease rate areas, you’re not picking up a lot of unknowns – so everything comes together that fomites aren’t a big deal. I'm not saying not to clean and disinfect. What I'm saying is don’t obsess about it, and absolutely don’t focus on this as your control measure. This is where we run into some places where they talk about, “Here’s all the stuff I'm doing to lower your risk. We clean and disinfect, we fog, and we do all this stuff.” Okay, fine, yeah, but what are you doing about ventilation? What are you doing about distancing? What are you doing about masking? If you’re doing a cleaning and disinfection in lieu of those, you’re wasting your time and your money, but if you’re doing cleaning and disinfection to complement those, great. That’s what we want. Don’t over-rely on it.
Ventilation – I'm learning so much more about ventilation than I ever thought I would. Ventilation is really the key to aerosolized pathogens. It’s obvious. There’s an “infectious dose” component. I'm standing here and I'm making this cloud of aerosol and we’ve got a good breeze coming through. We’ve got 80 km/hr winds outside right now (which is why I'm on a generator, because our power is gone). If I'm standing outside, there is no risk anyone is getting this virus from me if I'm infected. If I'm in a room with poor ventilation, the risk goes up. The longer I'm there, the risk goes up, so ventilation is really important. It disperses those clouds and reduces that infectious dose that you can run into.
Outside is great. There is very little risk being outside. The goal on the inside is to make it as close to outside as possible by maximizing the airflow. This can be liters per person per second, or this can be air changes per hour, or a combination thereof. Six liters per second per person has been mentioned most recently as our target for ventilation. This is a good general target.
Do we want it all recirculated air, or do we want fresh air coming in? In a perfect world, we’d have a lot of ventilation and it would all be outside air and there would be no recirculation. We don’t live in a perfect world in clinics, especially in cold climates. When it’s February here, we can’t bring in all fresh air because the HVAC systems won’t be able to keep up with the temperature. There has to be recirculation.
Recirculation isn’t the end of the world, because recirculation still dilutes. You take this high-risk area in a small environment, and we dilute it out all over the clinic, it’s probably not posing a risk all over the clinic unless you really have a super shedder event. Fresh air is good. More air movement is better. If we can get both of those, that would be great.
Airflow is really the key. Fresh air is better than recirculated air, but recirculated air moving really well is really important.
Then we get into filtering. Again, this is not an airborne virus that’s wafting around in the air currents and getting up in the ducts and going to the next room. If it was, we would have different epidemiology. We would see different types of exposures. Contact tracing would be a lot more difficult. This is that aerosol cloud droplet, direct contact.
Putting UV filters or HEPA filters in ductwork, which is really expensive, probably isn’t going to help us a whole lot because I'm not really worried about it going up in the ductwork and spreading around. We’re more worried about that in-room component.
There are a couple of things we can do about that. One is just to just move air. Fans in rooms can do a lot. Open doors. Fans can move things along really nicely. Then we can add HEPA filters to fans. These commercial, over-the-counter, HEPA filter fans aren’t that expensive. Whether the filter really helps a lot we don’t know, but they move air, which is really important. If you add a HEPA filter to that little unit you’ve got with it, then great. It’s probably going to help a little bit. The more we can put these into areas that inherently have poor ventilation or are otherwise high risk in some small spaces...take a really crappy exam room that’s small and poorly ventilated, open the door and toss a fan in there, you could probably drop that risk quite substantially.
There are more expensive approaches to this. UV or HEPA in ducts probably won’t help us a whole lot, but you can do top-of-room, in-room, and these types of systems.
These are ones that get mounted on the wall at the top of the room. These have been shown to have a pretty good effect for respiratory viruses of various sorts. They are more expensive. Whether they’re a really good bang for your buck is hard to say. If you’re in a high-risk area and you have to use a high-risk room, then that’s something to think about.
Move air and think about adding filters at the room level, not at the duct level – but dilution is really the key. The more we can move air, the better.
The other thing is HVAC can be really expensive. You’re probably not going to come in and change the ventilation of your clinic. Maybe we can increase the ventilation and we can change the amount of fresh air that’s coming in.
Assessing how much ventilation you have would be useful. It would be nice for you to know what your liters per person per minute or air exchange per hour is.
CO2 monitoring actually is a really good way to get a proxy for how good your ventilation is if you have occupied spaces, because if you have occupied spaces and your CO2 is getting to certain levels, you know you don’t have very good ventilation. You can buy reasonably good CO2 monitors fairly easily, and you can find some general guidance. There is not really a set threshold we want for this, but you can say, “Here’s what it’s like when there’s no one in there. Put some people in there and if we see this climbing during the day, then okay we don’t have very good ventilation. We have accumulation of CO2, which might just be accumulation of virus-dense cloud if we happen to have an infected person in there.”
It’s something to think about. It’s a cheap and easy thing. It also lets you assess something. It’s not going to assess the filtration component. You could put a HEPA filter in there and this won’t change. Your reception area or your treatment area and you’re worried about that – you can put a CO2 monitor in and see how high it goes compared to when no one is there. Now let’s change something. Let’s open a door. Let’s put a fan on. Does that drop it? Okay, great. That might be useful. This is maybe an easy tool to give us a little bit of guidance.
Q: When I looked at that study, the researchers stated in study that they purposely did the study in the dark, because they knew UV would 'retard the virus'. Not realistic.
Scott Weese: I assume this is the bank note study you’re talking about? Yeah, and that’s the whole content. You can keep things alive really easily in nice temperature-controlled, no temperature/humidity shifts, no UV light, and you can see great things. We actually did a study with Strep equi, (strangles in horses) a while ago where there were reports that this thing can live for days or weeks on surfaces. We stuck it on surfaces outside and it died within 24 hours because it was in the real world. We have to be careful about some of these in vitro things.
Q: One thing we always do is turn our HVAC fan ‘on’, not 'auto', so it runs and circulates all the time.
Scott Weese: Yeah, that’s a great, great point. Just making sure it’s always running. The more we can do to move air, the better.
Thinking about CO2 monitoring probably isn’t a bad idea because they are cheap and can give you a general idea of what’s going on, and if things are working, you can make changes.
This gets into the question I get every day. When should we let people in the clinics? When? If? How and maybe why?
There is no answer to that, because it really varies with a lot of things like your regional risk. How bad are things or how good are things in your area? What’s the likelihood that average person off the street is infected?
Clinic personnel risk factors – if you have a bunch of people that are just asking for serious disease, that’s going to probably change your approach to it too versus a lot of low-risk people.
Your clinic layout – how well can you make changes? This comes back to the Swiss cheese thing. If I can’t modify my environment very well, I need to do more things to keep that environment safe, which is not bring as many people in it.
Climate - if it's -20 degrees out, outside doesn’t work as well. If you’ve got better climate, you can do more things. You can arrange curbside easier and do outside appointments. There are a lot of things you can do when the weather is nicer.
Practicality of alternative approaches for your clinic or your layout: maybe if you don’t have parking, that changes some things. Right? What if people take transit and that’s how they get into your clinic? That changes how we manage people when they come in, so there is no one-size-fits-all.
Staff comfort is a big one. Comfort meaning their willingness or their freak-out factor that people are coming in – and people are scared. There certainly still is a lot of wariness in staff in some areas. Part of this we can counter by education. Right? Here’s all the stuff we’re going to do to reduce your risk. You’re at greater risk at the grocery store than you are at work, and that’s a big part of it, but we have to consider staff feelings as part of this.
For me, there’s also an ability and willingness to enforce the rules. If you do these things, you’ve got to do them right. If you know you’re not going to enforce it amongst staff, and you know you’re not going to enforce it amongst clients, then you’ve got to be more inherently strict because you’re going to break down your protocols by not trying to enforce them and creating a culture that lets all this stuff happen.
I mentioned the three Cs at the start. I hit Swiss cheese a lot, but back to the three Cs. The more we can think about those three Cs, the more we’re thinking about our control.
For me overall, there are a few things we’re trying to do. Limit the number of people that are ever in the clinic. Fewer people means fewer potentially infectious people, and fewer people that can get infected. We don’t want to be a focus of infection for health reasons, plus if you're a focus of infection, you’re getting more scrutiny and then you might get shut down.
Limit the number of people that are in the clinic at any given time. Less density means less chance of exposure, less accumulation of virus, and fewer contact points.
Limit contact between owners and staff, and with other owners. We want fewer people there ever – fewer people at any given point – and we don’t want them to be in close contact, so we’re starting to cover a couple of different scenes here.
Minimize contact times and overall time in clinic. Even if they’re by themselves, that overall time can create some risk because they’re potentially creating aerosol clouds that hover around them. It’s like Pig-Pen. Remember in Charlie Brown? It was the little cloud that wafts behind the person. That could potentially happen.
We want to maximize the use of barriers and ventilation. We want to do all these things while still functioning as a clinic. We still need to be able to provide care and survive economically.
For me, fewer people in the clinic really still should be the goal. It doesn’t mean no one necessarily, but it means fewer people in the clinic because it lets us do a lot of things. It’s fewer contact points. It drops the risk because we have fewer human-to-human contact points; we have less risk of an infectious person coming in.
The big one for me is this third one – it’s the greater ability to control things right in the clinic, because if I don’t have as many people in the clinic, I can choreograph the flow of those people much, much more easily because I have space to do it. If you have a lot of people in the clinic, or they’re coming in in an unstructured manner where the door is open and anyone can come at any point, I can’t choreograph that flow. I'm going to talk about that in a little bit, but I want it such that when someone comes in, they have to come in, they check in, a quick hi at the reception, they go into an exam room, they stay in the exam room, you grab the animal, take it to the back, we do our thing, reunite with the animal, and kick them out the back door. That’s gold standard for me. We can’t do that if everyone is coming in the clinic unless you’ve got a really big clinic with a lot of exam rooms, and most of us don’t have that.
The fewer people we have, the safer we can make it for those people that come in by decreasing the congestion that’s going to be there.
Allowing clients in the clinic for me means maximizing things to keep them out of the clinic, so maximizing telemedicine, default telemedicine. It can’t do everything obviously, but a lot of things we can still do by telemedicine.
Curbside – the more we can do that, the better.
Hybrid appointments I'll get to. This gets at not only fewer people in the clinic, but shorter times in the clinic and fewer contacts.
You need to think about patient housing. We can’t do curbside very effectively if we can’t house a lot of patients. If a lot of people are coming and dropping animals off, we have to think about how to repurpose some areas for housing. That might be repurposing the odd exam room into temporary patient housing.
It’s a really basic thing. This is a lot of common sense, but sometimes you have to step back, come into your clinic and just think of it from an infection control standpoint... or pretend you’re a virus. How are you going to get around?
Basic concepts – hand sanitizers, masks at entrance; hopefully people are wearing their own mask, but if not, something is there for them.
Rework your layout. The less people have to think, the better you’re going to do. The less people that have to actively comply, the better compliance you’re going to get. If I walk in and things funnel me to go this way, I'm going to go that way. I'm not going to step over a table. I'm going to walk along it. We will take the path of least resistance. Make a change in the layout of the reception area so people flow the right way. Move or take away seating space so people don’t congregate close together.
Direction of flow indicators – you can do that too.
Plexiglass barrier for reception is pretty standard.
Changing seating and limiting seating.
One thing we forget about sometimes is in-clinic transmission. If you look at human healthcare, one of the big concerns is that a lot of the transmission that’s happened in human hospitals for healthcare workers has come from other healthcare workers. It’s not coming from patients. PPE works, so they’re finding that people that worked on COVID wards in some studies haven’t had a higher risk of COVID than people that didn’t work on COVID wards or didn’t have any patient contact. They were getting infected because they were getting lax in lunchrooms, meeting rooms, and spaces that are not patient areas. We have to think about our staff as well. One infected staff member can and absolutely will shut your clinic down. I've seen it many, many times.
Distancing staff members in the front office.
Exam rooms – like I said before, for me exam rooms are client-holding rooms in the best-case scenario. They come in and they go right to the exam room. I don’t want to be in there more than I have to be, so I come in (ideally I've gotten a history before, but I come in), the door is open, maybe there is a fan on, I say, “Hi, how are you doing? I'm going to take your [whatever] to the back and we’re going to do our exam. Any questions? Okay, we’ll see you in a couple minutes.” We do our thing, bring it back out, here’s what we found, and here’s what we’re going to do. If I have to demonstrate something, we can do it at a distance, so we can handle that component. We can have the door open maybe. Handle another component of those Cs. We keep that contact time down as opposed to hanging out in the exam room where the client inevitably is going to drift closer and closer to your face when you’re doing things, and they’re going to come help like they always do, and you’re going to end up six inches away from this client despite having the best intentions not to do that.
We can do this if we don’t have a lot of people coming in because we can put them right into an exam room. It’s good to think about exam rooms as client waiting rooms and not exam rooms. Try to separate that.
Treatment areas – this is where we get into our staff-to-staff transmission. For spacing, think about how tables are. Think about how people have to congregate and how people have to move. We can do treatment areas with fairly low risk. They tend to be fairly open spaces, but we just don’t want to have a lot of crowding. We don’t want people having to congregate together. If you’ve got two computer stations where people are doing data entry, you don’t want them right side by side (which they often are). You separate them by six feet. We’ve removed people that might have spent a lot of time right next to each other doing medical records or looking things up, so the more we can space those things out, the better.
Exit – I don’t think this is the end of the world, but the more we can prevent crossing paths and contacts, the better. If they can go out a side door or go out the back door, that’s perfect. If they have to go out the front door, that’s not that big a deal. We see this in stores all the time. If there aren’t a lot of people coming and going, the risk of them contacting someone is very low. The more we can make a one-way flow, the better. It works well in some clinics and it doesn’t work in others. That is where you think about your clinic. Think about how we prevent them from having to come back and at least hang out in the reception areas. If we can, bill them out online or bill them out in the exam room so we don’t get a bottleneck of people.
Offices and lunchrooms – whether it’s scheduling, spacing, creating different spaces, or repurposing rooms, this is where you get the risk because you take your mask off to have your coffee break or have your lunch, and you end up chatting for a half hour or whatever. Then we’re getting all these Cs coming in. We have close contact. We’ve lost our barriers. We’re in maybe a closed space. We’re doing things that generate aerosols, and that’s what we want to avoid – which is a challenge. You want to talk to people. You want to interact. You want to discuss things. We need to figure out how to space that out more. Keep those to a minimum. There are certain times we’re going to have to be close to personnel/other staff and we want to. We just don’t need to do it all the time. If we can make sure that those times are required as opposed to if I just happen to be sitting here reading something, relaxing, or eating, and you just happen to be sitting here 3 feet away from me, well, we can easily just do that 10 feet away. It’s not going to hurt either one of us and it’s going to reduce our risks.
I'm just going to check the chat here.
Q: Has there been an infectivity study done yet? Like an R number? With masks and without masks? Thanks!
Scott Weese: If you’re talking about Rt... so R0, you hear about that a lot. R0 is an inherent characteristic of a virus. That’s how many people the average infected person infects. With this virus, it’s about 2.2. Rt is the actual one, so what’s in the real world. Things that we do drop Rt. What we’re trying to do is drop Rt down below 1 and the outbreak dies out.
I haven’t seen controlled studies because no one is really going to do a controlled study of masks and no masks. We have certainly a lot of experiential data, a lot of data from other types of observational approaches where mask use has resulted in a decrease. We have data comparing different countries. We have comparing different approaches within countries. We have complementing in vitro data and aerosol generation studies, and you put them together and we can be fairly confident they work. There are modeling studies that will look at that. What masks will do predictably is draw up Rt 0.3 or 0.4. to give an example of one study I remember seeing.
Again, it’s the Swiss cheese approach. If the inherent R0 of this virus is 2.2, if I drop it to 1.9, I'm going to slow it down. It’s not going to help a whole lot, but if it’s 2.2 and I drop it a bit by spacing, and drop it a bit by keeping sick people at home, and I drop it a bit by more and I can get it down to 1.2 or 1.1 – which is where a lot of places have it when they’ve still got exponential transmission with moderate control measures – that 0.3 difference might be the difference between ongoing exponential growth and the virus dying out. It does have an effect. It’s got a modeled effect. I don’t think we have controlled studies that have shown what it is, but we’ve got a few different models that would give an idea what it might be. That’s a pretty vague answer.
Reducing staffing numbers – it comes down to how do we reduce contacts. How do we allow ourselves to space things out? Reducing staff numbers doesn’t mean fewer people working. It means fewer people working together. That could be fewer people in the clinic. It could be fewer people in the same place in the clinic. It could be spreading out areas. It could be spreading out reception. It could be spreading out how things are done in the treatment rooms and lunchroom. It could be having people that are doing management duties and people who are doing callbacks and people who are doing records and telemedicine and doing that at home. They're doing normal work, they’re just not in the clinic, and they don’t have to worry. Two vets are off doing things at home, then that’s two fewer people I have to find space for in the clinic. Those are the things we can do. By maximizing all those other things, we can make it easier to do things right in the clinic.
Telemedicine – if this doesn’t change our approach to telemedicine, nothing will. Telemedicine helps us drop the number of people that are in the clinic. Also, it lets us shorten the time that they have to be there. It lets us reduce the DVM footprint. It lets us reduce the number of people in there and lets us speed up things through hybrid appointments (and I'm a big fan of these).
Again, we want to reduce the numbers of people that are in there, but we really want to reduce the time that they’re in there if they’re going to be there. We can take a long appointment and make it a short appointment, or we can take an appointment where we need to talk to people and turn it into a curbside appointment where we don’t have to have them in there.
Just as an example, a new puppy visit – I want to have a talk with them. I want to have a good discussion about nutrition, preventative medicine, and everything else. We can do that by telemedicine. We can have a long chat and get all those things done. You’re coming by tomorrow. We’re going to do a curbside. We’re going to give your puppy a physical exam. We’re going to vaccinate it. We don’t have to have them in the clinic.
If they have to come into the clinic, we can do it really quickly. We’ve done all this discussion. We don’t have to create that risk in the exam room. We just have to get the animal, take it to the back, do our exam, vaccinate it, give it to them, and kick them out the door. The more we can use remote approaches to reduce the number of people and reduce the time that they’re in the clinic, the better. I think hybrid appointments are really a good way to go.
We can do follow-ups sometimes to avoid having them bring them into the clinic. We can do some evaluations with phones. You can just look at things. If someone is worried about a wound, the first step might be looking at it, but the more we can bring a telemedicine component and drop the time or the numbers, the better.
Contact tracing – it is something you might have to think about depending where you are. It depends on your regional control. This is something we’re going to have to think about in Ontario in certain zones. Retail is being required to do this, and it’s still a bit unclear what that means for veterinary clinics.
It’s never a bad idea to have contact tracing. In some places, you might have to have it to be open, especially if things change and people get more restricted. It’s worth thinking about now, because all of a sudden you get a mandate saying that if you’re going to be open, you have to be able to contact trace. It’ll be good to put some thought into it. It might be that you’re writing it down in a book. Here’s everyone that comes in the clinic – clients, delivery people, whatever it is. It might be using your medical records system to do it, and then having something else for the staff. You might be using a QR code that people scan at the door, and if you don’t scan, then you record them. There are various approaches that can be done.
Think about what you can do. Hopefully you won’t need to use it, but you might.
Then any other means you have to identify risk and identify contacts. This varies by country. This is an example for Canada. We have the COVID Alert app. What this does if you have it on your phone, it sends out these anonymous pings. If it’s close to another phone, it realizes that and they exchange information, but it’s all anonymous. It’s all private and no one ever knows what it is. If I've got this on my phone and I'm identified with COVID, I can put a code in my phone and that will notify everyone whose phone has been in contact with my phone. It will just say, “You’ve been in contact with someone positive. Get tested.” It won’t say “Weese gave data.” There is no additional information.
This isn’t available everywhere, but if you have access to this, I would strongly recommend you use it. Whether you can make your staff use it, I don’t really know the legal aspects depending on where you are, but I would strongly recommend your staff do this. If you get a positive staff member, you’re into a wreck, right? You want your staff to be protected as much as they can be to protect you. The more you can bring in tools like this that you have available to you...I’d rather see this done by discussion and talking to people. “Here’s why we need to do these things, because we don’t want to be shut down. We don’t want to get people sick. We don’t want to kill so-and-so in the back room there, so let’s do some things. Let’s be responsible” as opposed to “Thou shalt do this.”
Think about the options that you have, and have good discussions within your clinic about personal responsibility and protection, because your 22-year-old technician might think they’re very low-risk for getting seriously ill (and they are), but your 65-year-old receptionist with diabetes might not be, so we need to think about everyone else around and your clients.
Vaccination – the only licensed vaccine right now is still Sputnik, which was licensed in Russia without a ton of data. I'm not sure I would allow them to vaccinate me with it, and most people probably wouldn’t. It’s being used in a couple of countries now. They are coming out with more data. Their phase 2 data was met with a bit of skepticism based on some strange results. It may very well work. We really don’t know.
There have been reports of vaccine studies being paused. There was just one the other day, a Brazilian study with the Sinovac vaccine I think it was. It was paused. What this tells me is the system is working. Right? Someone gets sick in a vaccine trial, they’re going to pause. It doesn’t matter what it is, they’re going to pause, and they’re going to figure out what it is. It means that they’re not trying to rush these things. I think pharma is doing a very good job. They want to push it through as much as they can, but I think they realize that they have to do it right. We’ve got one shot at this for a lot of people. If we screw up the first vaccine, good luck getting other people to vaccinate. The number of people that say they’ll get vaccinated is scarily low. If we screw up the first vaccine, it’s going to be abysmally low.
You’ve probably heard of Pfizer’s vaccine. Early estimates based on fairly small numbers indicated 90% efficacy, which is really encouraging. It needs to be stored at -80 Celsius, which is really not encouraging. Pfizer's been buying up -80 freezers. This is going to be a big problem for distribution if this is the vaccine.
For me, the biggest story from this is that vaccination might be really effective, at least in the short term. Whether it’s Pfizer’s vaccine or some other vaccine, it means this is a potentially a vaccine-preventable disease – because we haven’t actually known that.
This vaccine has to be in -80C or on dry ice, which brings in a lot of distribution issues. It really brings in distribution issues into rural areas, under-serviced areas, and developing countries. We cannot control this virus by vaccinating people in the U.S. and Canada and rich countries in Europe. We cannot control a pandemic that way.
There are a lot of issues here, but it’s quite encouraging.
We won’t really talk about these guys. There are a couple of groups looking at sniffer dogs. I'm working with some of this, trying to see if dogs can detect some volatile components that are produced when you’re infected with this. There’s a lot of interest in the airports. I'm actually more interested in things like homeless shelters and migrant farm populations, where they might be able to go in and signal off for really dense environments saying that we need to test these people.
That’s something you might hear about and people might ask about it. A dog’s nose is a wonderful thing. Whether it will actually work, we’re still not completely sure, but it’s pretty cool stuff.
With that, I'm happy to take questions as long as you want. I don’t want to keep you any later on a late night already. If you have any questions, as always I'm always happy to take them. If it’s an urgent question, put “urgent” in the title of the email. I miss them sometimes, but if I don’t follow up quickly, send me another email to chase me. Never hesitate to contact me about these things.
With that, I think we have another question or two.
Q: Any comments on the rapid tests reliability?
Scott Weese: It depends on the test. Rapid tests are meant to be screening tests. They're not PCR. I've got a slide in here on that, I think.
Rapid tests can be better than PCR in some ways and worse than PCR in some ways. Rapid tests are meant to be really easy. The ideal rapid test is something you spit in, like a SNAP test that you can spit on, so something you can do anywhere. A rapid test that needs a lab technician doesn’t really help us. A rapid test that anyone can do, so you can go in and you can test 500 people at a meat processing plant, or you can test whenever really quickly – that’s where we’re hoping these things will work.
Inherently, they’re never going to be as sensitive and specific as PCR...well, not never, but they usually aren’t. It’s a battle of what do we want. When we’re looking at populations, we can accept that. If we’re going to test a lot of people and we just want to know if there is a problem here, if it’s only 70% sensitive, we’re going to miss 3 out of 10 positives, but we’re testing a lot of people and we’ll probably know if there is a big issue there. If it’s an individual person we’re trying to sort out, we probably don’t want a rapid test.
Testing is really useful. You can’t test your way out of an outbreak. The White House showed that perfectly. Strict reliance on testing over other things didn’t work. Rapid tests have a role. They are not going to be the sole thing.
I guess what this slide shows is that the good thing about rapid tests is they tend to be most useful right around that infectious period. With PCR, you can get prolonged positivity which creates some issues, so you have people who are PCR positive and they’re no longer infectious because it is a very sensitive test.
There are some really good things about rapid tests. How we’re going to position them is hard to say. It depends on how cheap they are, how quick they are, and whether there’s any technology required, but really I think they’re mainly going to be used in high-risk situations. You can see it when people are going to get on a plane. They are not 100% so that decreases a little bit, but if you’re going to identify the odd person that gets on a plane that’s infected, that’s good because the implications are very high.
There are various situations where rapid testing might be useful.
Q: Antibody test reliability?
Scott Weese: It just depends if you’re talking about animals or people. I guess regardless, tests can be fine. It depends on what you mean by reliability. Does the test detect antibodies? Yeah. There are a variety of tests that are out there that are pretty good. Now, what does that mean? With the test, antibody cross-reaction with our common cold coronavirus doesn’t seem to be an issue. Cross-reaction with our feline coronavirus when we’re looking at cats doesn’t really seem to be an issue if the test is developed properly.
It’s what do you use an antibody test for. An antibody test isn’t going to be used for diagnosis of disease, at least at this point. Maybe you get an IgM test, but an IgM test is not going to kick in until...by the time you get IgM, you’re probably not infectious anymore, so it’s more of an epidemiologic test.
Antibody tests might be useful if we’re trying to say if someone is susceptible to the virus. The problem is we don’t know what that means right now. I could have antibodies. Does that mean that I am resistant to infection again? We don’t know. There are still a reasonable number – a small number, but enough people that have very clearly confirmed second infections that show there’s at least antibodies. We don’t get complete protection. People can have antibodies and they can still get infected, and they get a big antibody bump when they get the second infection. Antibody tests are good epidemiology. We’re using them for screening animals that have been exposed. We’re trying to say yes/no/were you exposed in the past, and that’s all we’re trying to say.
With antibody testing, if you’re looking at trying to get the scope of what’s going on and trying to get a historical issue where this has been useful for blood donor screening, for example – not to see if the people are sick, but to get an idea of what the prevalence might be in the population. If we’re going to test a bunch of people that donated blood because we’ve got the blood, then we’ll say 3% of those were positive. That gives us an idea of the historical prevalence. It’s not really going to be used much as an individual person thing at this point. Six months ago, people were talking about these “immunity passes” you can get. You’ve got antibodies so you’re good to go. You don’t need to wear a mask. You don’t need to do anything else. We don’t know if antibodies protect enough, and we don’t know that you can’t get it again, so that’s largely gone off the table now.
Over time, we’ll see what antibodies mean. The tests are fine. It's the interpretation that’s the challenge.
Did I get through all the questions? I think there aren’t many. I probably got through them all. If there are any other questions, feel free to toss them in there. Like I said, don’t be shy to email me if there are any questions, if you’re in a clinical situation that you have concerns about or you’re worried about them.
Q: Have they seen a trend to how long people are asymptomatic carriers yet?
Scott Weese: I guess that just means how long the infectious period is.
This slide I think shows it fairly well. This is in weeks, is the big thing I notice here. We’ve got a fairly defined period. Generally, we think that the peak infection period is right before you get sick and right after you get sick. When you’re asymptomatic we don’t have that same reference point, but it’s probably a similar duration of time. If you’re clinically ill, you’re going to be pumping a lot of virus a day or two days before with the peak virus right around the time you get sick, and that’s going to decline fairly quickly, and by a week it’s pretty much inconsequential.
Asymptomatics probably have a lower magnitude of shedding. It seems they have a lower magnitude of shedding. The duration is probably a little bit shorter, but it’s probably within that same window. Again, we don’t have pre- and post-illness, but we’ve got a 7 or 9-day period where we’re worried about it.
If you look at the guidelines for isolation, what we say is if you’re infected, you isolate (most places) 10 days from the onset of clinical disease or your positive test, because the shedding period starts a little bit before you would be sick or you’d be tested, and then it stretches out for maybe a week after that. Ten days gives us a cushion.
If you’re exposed, we say 14 days because that curve has just been shifted a few days because you didn’t have that start point when it took a few days to get sick. I probably didn’t explain that very well. Essentially, the take-home would be that if you’re an asymptomatic infection, you could be shedding anywhere from basically like not at all in terms of infection risk to probably 2, 5, 7 days maybe. Some people go longer. This gets into the whole concept of a super-shedder.
I've got a slide here.
There are some biological super shedders. This is a really weird virus. I mentioned the R0 is about 2.2 or somewhere in that range, so your average person infects two or so other people. The thing with COVID is your average person actually infects no one, and some people infect a lot.
This is a good example of a super shedder. This is a person who caused an outbreak at a church service. You can see he infected 54 people, I think it was. Thirty-five of those infected no one. Most of those just infected a household contact. A few of them infected a couple. This dude infected 50-some.
There are some people that are biological super shedders so that when they breathe, they produce more virus than someone else does when they’re sick and they’re coughing and sneezing. They produce a lot of virus. Some of it is behavioral. They're in church and they’re singing and they’re not doing other things, so they’re creating a risk behaviorally.
Where I was going with the asymptomatic side is that some people could be asymptomatic but be a super shedder. They're producing a lot of virus. You just don’t know. The only way to find a super shedder is to find a super shedding event that’s already passed. This is why we still worry about routine practices.
The long-winded answer to your question is your average asymptomatic person is probably going to shed for a few days at a lower magnitude of virus than a person with clinical disease, although some of them might pump out a lot of virus and do it for a bit longer.
Carla Burris: It looks like that was all the questions. Again, thank you to everyone for joining us on a Sunday evening.
Scott Weese: Thanks a lot, everyone.