麻豆传媒

Topic: Asymptomatic Transmission and Reinfection

Emerging data shows more risk of asymptomatic transmission and reinfection with COVID than previously thought. Experts will discuss these findings and what are the implications for managing the pandemic. 

Who:

• - Professor of Medicine and Epidemiology, Vice-Chair of Medicine for Healthcare Quality, and Director of the Laboratory of Mycology Research -  UT Health Science Center at Houston.
• - Professor and Chair of the Department of Molecular and  Cellular Biochemistry - University of Kentucky

When: July 16, 2020. 3PM - 4PM EDT

Where: 

This live event will also be recorded and transcribed for use by media and communicators after it is concluded.

Thom Canalichio: 

We'll go ahead and get started. Welcome to today's 麻豆传媒 live expert panel. Today we're going to talk about a couple of big topics asymptomatic and pre-symptomatic transmission, the possibility of reinfection and also the transmission of the virus and whether or not it can be described as airborne. We have with us two panellists. We have first – I’ll spotlight his video, we have Dr. Luis Ostrosky. He's professor of infectious diseases at the McGovern Medical School at UT Health in Houston.

And we also have Dr. Rebecca Dutch. She's Professor and chair of the Department of molecular and cellular biochemistry at the University of Kentucky.

Thank you very much for joining us panellists, and I'd like to start off with a question for both of you about the anecdotal reports about the possibility of patients getting re-infected. Dr. Ostrosky How can you explain that for us? 

Dr. Luis Ostrosky:

Thank you very much for that question. So we've heard through media mainly about patients that have been sick for a while, they improve and then they get worse again, and they test positive and it's really hard to tell from this media reports if this is just long term shedding of the virus and sort of long term symptoms, which we're learning that that can happen. And this is what's happening, or if it's really people that are getting actually re-infected or relapsing with the disease. So, I think it's too early to tell whether you can actually get re-infected or relapse. We have not seen this described in the medical literature. It's mainly through media that we're hearing about these cases. 

Thom Canalichio:

Dr. Dutch, tell us a little bit more about how we can differentiate between these two questions that Dr. Ostrosky mentioned people who may not fully clear the virus and still test positive versus the possibility of getting sick a second time. How can we tell the difference? 

Rebecca Dutch:

Oh, that's a great question. So, we do know that some people when they're infected are maintaining positive RNA for a long time, they can go weeks to months. So, one way to do that would be - so that that's a good possibility for what might be looking like a reinfection. If that's true. One way to do that might be to look over time and see what two things are, what are the viral sequence in there - we have the ability to sequence these viruses, are you getting something different or does yours look exactly the same?

The other thing is to look at the timing between these - and this will be much more readily available or much more doable as time goes on. If someone who seems to have cleared the viruses, had multiple negative tests and then comes back infected nine months, 12 months later, that would suggest - be more suggestive of reinfection than someone who a few months later without being 100% sure has cleared the infection is re-spiking sequences. So, I think it's something that we absolutely need to keep looking at. I completely agree with Dr. Ostrosky on this. It's something that we will learn more over time but again, it’s a little challenging to answer the question when we don't actually have - we don't have actual written reports of this. We simply have a few people who are making anecdotal stories about seeing a potential reinfection. And it -we won't know for sure. We do know with some of the human cold Corona viruses, that over time, you can get re-infected. However, we also know that with the people infected with COVID, they mount - most of them mount at least some kind of antibody response that does wane over time, And the newest report suggests that people are all mounting a pretty good T-cell response which would suggest that they are developing protective immunity at least for a period of time. 

Thom Canalichio:

So Dr. Ostrosky we just heard from Dr. Dutch that to know the situation well, we may need to follow patients for nine months or a year. We're only four or five months into this year in the US, therefore, what does that maybe tell us even though it's quite early about how the possibility of reinfection -what that sheds light on in terms of how a potential vaccine might work? Are we are we seeing early indications of a waning immune response even for those who have effectively fought off of the virus? And does that mean that we might need regular boosters once a vaccine is out there? 

Dr. Luis Ostrosky:

So, as Dr. Dutch mentioned very clearly, we know we mount an antibody response, there's some reports starting to come out that this wanes over time, over a few months. And on the other hand, we have other reports that are mentioning that antibodies are not everything, it's T-cell dependent as well. So, your immune system cells are trained to respond to this virus. Again, early to tell what's going to be the sort of the play out of this situation, but if it behaves like other respiratory viruses and it doesn't mutate too much. I assume that we'll be able to have a vaccine that works for a reasonable period of time. 

Thom Canalichio:

And Dr. Ostrosky, if it does turn out possible that someone gets infected a second time, would they hypothetically be able to also transmit the virus again? Or is that likelihood less? 

Dr. Luis Ostrosky:

So, if that happened, we were able to document that this subjects would more likely be transmissible again. So, but again, we have no evidence in the medical literature that that has occurred.

Thom Canalichio:

So, there's certainly a lot that we just don't quite know. I want to ask Dr. Dutch. With all of these question marks, what recommendations should people be following to take precautions if they've had the disease to avoid the risk of reinfection for themselves or not to pass it to others?

Rebecca Dutch:

Well, I think we're all wise as to assume that we could have this virus at any time, and we could catch this virus at any time until we have good evidence from the literature to prove that otherwise. And that means following the precautions that we are trying widely to distribute, put your mask on, have everybody put masks on, keep social distancing. Those things really matter. And I would make the assumption that it's possible to get something back even if you had it. So just go ahead and take the precautions. I still think it's likely that we're generating protective response for most people, that the history of respiratory viruses would suggest that's the most likely scenario. But given how recent this has come up, and how much we don't know, it's always wiser to be erring on the side of caution.

Thom Canalichio:

The more unknowns the more caution that's called for. We have a question from Tina at Science 麻豆传媒. Tina, I want to make your audio live and give you the chance to ask this if you'd like – Tina, go ahead. 

Tina:

Yeah, Dr. Ostrosky you mentioned that antibody responses seem to be waning over a few months or so - is that necessarily a bad thing? I mean, isn't that something that happens normally when you catch a cold or something? And Do you need the antibodies to stay high in your blood to get protection or do you just need memory B-cells that can then crank up antibody production if you encounter the virus again? 

Dr. Luis Ostrosky:

That's a great question, Tina. And the thing today is we just don't know - the reports that are sort of bringing forward the winning antibody titers are coming mainly from China at this point where they've experienced the infection before all of us. And they're noting decline in antibody titers, that's about four months out. But like you say there's other possibilities, there's a possibility to reactivate those B cells or T-cells that are going to be working there. We just don't know this is a virus that's brand new to all of us. All of us have known this virus for about eight months now, that's the most we've known about it. So, a lot to learn. 

Thom Canalichio:

We have a question from Emiliano Mega from Salud Con Lupa about asymptomatic cases – this is the next topic that I want to get into. Emiliano, would you like to ask your question? 

Emiliano:

Yeah, thank you so much.

So, I think I have two questions. Actually. I was wondering whether asymptomatic people also develop kind of lung damage and also this overactive immune response that we see in patients with symptoms. Like what do we know about that so far?

Also, my next my next question is, and I'm sure this may not have an answer. Do we know what makes certain people more likely to get the virus and not develop symptoms? 

Thom Canalichio:

Thank you, Emiliano. Dr. Dutch, would you like to take the first question? 

Rebecca Dutch:

Sure, let me start with those. First of all, in terms of the first one - can asymptomatic people actually being having some kind of damage go on. There are some reports that suggest that can be the case that sometimes people will not feel that they were ill, but that if you actually went in and did careful analysis of their respiratory tract, etc, you can see some damage that would be consistent with a viral infection going on. So, some asymptomatic people may simply not be perceiving that those changes are going on and not be getting ill enough that they notice it. So, you can't rule out the possibility that someone might have some longer-term issues that they're dealing with because they had the virus but weren't aware of it.

In terms of things more likely to make us asymptomatic or ill. The small amount of stuff I've seen on this would suggest, for instance, age is one of those, there was a report out of South Korea that suggested that younger people just as they're more or less likely to get really ill, they're also less likely to feel ill enough to think they have anything. So, they're more likely to be asymptomatic, older people are much more likely to have symptoms when they catch this virus. So that would be one of the things that we would be looking at. I believe those are the two questions - did I miss something else? 

Thom Canalichio:

I think that was everything from Emiliano about this. And we talked a little bit about the asymptomatic and pre symptomatic cases being a major topic that we wanted to tackle today. So I'd like to follow up with you about that, Dr. Dutch - what we've seen is a lot of data and recommendations changing regarding the threat of asymptomatic people spreading the virus, what's our current best understanding about that for whether or not that's true or also when the virus is most infectious - send I think we'd go from there. 

Rebecca Dutch:

Okay, so and I realize this has been an area of some confusion. Last month, there was a report that seemed to come from World Health Organization saying there wasn't an issue with asymptomatic spread. They retracted that the next day because scientifically that doesn't seem to be accurate, and it may have just been a misinterpretation.

The evidence suggests that people who are asymptomatic for the small number of studies where you've been able to follow them are replicating virus in their airways and have infectious particles that could spread. So far all the evidence suggests that people with asymptomatic infections are capable of spreading the virus. If you look at - for any person when we're most infectious, it fits with what we see for many other respiratory viruses. And unfortunately, what that means is you're actually most infectious before you even know you're sick, which can make it really difficult. The same thing is true with flu. The day or so before, you know you have symptoms you're already very contagious. With this virus, it looks like the few days before symptoms show up is when you're peaking the amount of virus in your upper respiratory tract and that's what you would cough out or breathe out. So that would be your infectious particles. So, it would seem like asymptomatic and pre symptomatic -which is people who will go on to generate symptoms are likely both sources of transmission. 

Thom Canalichio:

I want to dig into this topic just a tiny bit further and then I'm going to call on one of our freelance media in the audience for her questions, but I want to ask a little bit more about this and to Dr. Ostrosky that period of time that number of days pre symptomatic or obviously if they never develop symptoms asymptomatic. Is that a-typical in Corona viruses or other respiratory viruses? Or is that period of time much longer than other kinds of infectious disease that we've dealt with before? 

Dr. Luis Ostrosky:

That's a very good question. I mean, it's exactly as Dr. Dutch described it, the period we’re probably most contagious is the 48 hours leading to when you become symptomatic. So, if we looked at a curve, you would peak sometime around the time you actually become symptomatic. But those 48 hours before you're already shedding active virus, and then your curve starts going down dramatically up to the point where at day eight or so you're really not shedding enough virus to be infectious. And if you detect RNA, it actually has translated into not being to even culture a virus in cell culture. So, this is fairly typical of respiratory viruses, nothing strange or abnormal going on here. It's just really difficult when you are testing somebody who doesn't have symptoms, to know if they're in the upside of the curve or if they're already coming down. And that makes a difference to classify them as infectious or not. 

Thom Canalichio:

So, correct me if I'm wrong, that's at least twice as long if not longer than the infectious pre symptomatic period for influenza, right? 

Dr. Luis Ostrosky:

It's about the same, it's about 48 hours. 

Thom Canalichio:

It is about the same. Okay. That's helpful to understand. I think that there's been certainly a lot of confusion about when people are contagious, and the the risk of spread before someone even knows they're sick being a major cause for concern. I want to call on Charlotte Libov, go ahead with your question, Charlotte. I'll make your audio live. Go ahead. 

Charlotte Libov:

Okay. Thanks Thom. Um, my question is a little off topic, but I want to take advantage of having these experts here. And I'm coming into you from Florida. So, we're obviously very concerned and what I wrestle with constantly is trying to convey to people how deep the concern is, you know, what we really do have to be worried about. And last night, I noticed one of the trackers I followed had started a new category for Florida, and the other 24 states where the disease is spreading a lot. Previously, they had colours that denoted trending better – caution, warranted and trending poorly. And I see they have just added uncontrolled spread. And I didn't want to just throw that up there without telling people what it means. So, could you tell - because when they hear pandemic, they already know it's spreading? How do I convey this extra level of caution to them? 

Thom Canalichio:

Dr. Dutch, would you like to take that? 

Rebecca Dutch:

I can try obviously; I don't know exactly their definition of uncontrolled spread. What happens is you get more and more cases within your community and because each case can transmit to several other people, the average is thought to be with each person transmits  to  two to three, that's an average, but it can, we have some super spreader events that can go even more. As soon as you get enough of your population infected, the chances that you'll run into it when you're out go up and up and up. And I would consider that was what you're meaning with uncontrolled spread. It's not sporadic that you hit run into someone. It's actually much more likely.

I would add though, because I'm a virologist by training, so I study emerging respiratoy viruses and the molecular details of infection, so I should check with Dr. Ostrosky to make sure that that's how he would define uncontrolled spread. 

Dr. Luis Ostrosky:

I would love to see that metric. The way I would interpret that is when you have spread that exceeds that public health capacity to track and isolate and do contact tracing. Right? That would be my definition of uncontrolled spread when we've exceeded all normal ways to track and control the disease. 

Charlotte Libov:

And so how do I convey to people that this has just upped your danger of being infected -more than it was? 

Rebecca Dutch:

That's a wonderful question. So, I'm sitting one month from opening the University of Kentucky to 30,000 undergrads and trying to figure out how to make sure they take this seriously. I think one is this issue of relating it to how frequently they're likely to be running into an infected person. I think that many people have thought this was rare - that there's no chance I'll run into it. But realistically, if you were living in some of these states, and particularly some of the communities, you're going to run into this a lot. I know in New York – just last week there was a report that one of the areas of New York which I think is actually called Corona, it's a borough of New York, something like 68% of their population test positive for the antibody now, that tells you that moved into that community and it's spread incredibly widely. And if you are in places like Florida, I have a son in Texas and a son in LA, it's spreading there. And when you go to Kruger, when you go to everywhere, you almost for sure are running into people who have this. When you have high rates of spread going on. That'd be the first thing.

The second thing is to make them look really seriously at the hospitalization rates and the status of your intensive care. I always say to my kids who are in their 20’s and are healthy, you'll probably be fine. You might actually have some lung issues for a while - some people do, but you'll probably be fine. But if your ICU is swamped and you get in a car wreck, you might not be fine. If your ICU is wrecked and the neighbour that you accidentally guide this virus to needs treatment, they might not be fine.

So, we need to start thinking about each of us taking response of protecting not just ourselves, but our communities. And that's a hard message to get across. But I think it's an important one. 

Thom Canalichio:

Thank you for your question Charlotte, we'll come back to you for another one. I want to let another question come up first, though, because it relates to something that was mentioned in Dr. Dutch’s answer – Benita you had a question about antibodies, please go ahead. 

Benita Zahn:

Yes, I do, given that the antibodies may drop off, but the B and the T-cells would have memory. Is there any way to measure that especially in someone who may have been infected that they had a mild symptom, they didn't get a positive test? So, is there any way to determine if that person may have some ongoing protection? 

Rebecca Dutch:

So, the rough answer is yes. But it's not Yes like you could go to Walgreens and do this. So, the antibody tests that have been developed are getting more widely distributed - T-cell assays can be done – they're in the reports that go out - we have a lab at the University of Kentucky that can-do T-cell assays on patients. But they're much more specialized and they're not developed in any kind of kit or assay that the clinical lab is doing right now, as far as I know. So, in terms of studying this, yes, in terms of on an individual basis, going to get that answer somewhere quickly. Not as far as I know. 

Thom Canalichio:

Dr. Ostrosky anything you'd like to add to that? 

Dr. Luis Ostrosky:

Yes. Again, this unfortunately is a lot more labor intensive. It requires kind of a research lab setting. And it's going to take many months before this is commercially available, if it turns out to be useful at all. 

Thom Canalichio:

Thank you for your question, Benita. From the newsroom there at WNYT- NBC in Albany. Thank you.

Charlotte. You have another question I believe you'd like to ask. Go ahead.

Charlotte Libov:

Yeah, again, a little off topic.

I think there's been a lot of concern about the numbers that Florida is reporting and one thing that is confusing is the issue of diagnostic tests, antigen tests and antibody tests, and I was just sort of trying to take a quick look, I didn't get a chance. But I think the issue was that Florida had just started combining diagnostic and antigen testing and that's not necessarily a good idea. Can you tell me about that? And then also explain if there's a difference between antigen and antibody testing, or if those are interchangeable. 

Rebecca Dutch:

So, let me just briefly tell you what the three tests are. So, the diagnostic test you're describing is actually looking for the RNA in the virus. So, these viruses have an RNA genome - we have something called DNA as our that carries our genetic material. Coronavirus has never used DNA, they use RNA. And so that test is looking specifically for whether RNA from the virus is present in the person. And usually with a nasal swab sometimes down the throat. The antigen test. So, antigens are parts of the virus that your antibodies are interacting with. So, the spike protein on the surface is a very common antigen that is going to be bound by those antibodies. So those are tests that look for essentially primarily viral proteins. So, combining if you had the same patient, they likely would be positive on a diagnostic and an antigen test because both look to see Is there a virus present in your body. You might have patients stay longer diagnostic because they have viral RNA but not a lot of particles. But combining them might well double count.

This other one you're discussing is antibodies that looks to see whether a patient's system has generated antibodies that recognize a virus. So that's a test to see. Have you been infected and mounted an immune response? So that's a very different type of test and you'll stay antibody positive generally, hopefully for a long time, we're still figuring it out, but at least longer than for most people, then you would stay RNA or antigen positive. 

Thom Canalichio:

Dr. Ostrosky Is there anything you'd add to Charlotte's question about the testing? 

Dr. Luis Ostrosky:

Yeah, so combining molecular antigen and antibody testing is problematic because you're basically adding into the basket, active infection with evidence of previous infection. And you may have overlapping patients in that same bucket. So, unless it's very, very well done, excluding duplicates, and looking at timelines of things, it is problematic and it may not be able to allow us to compare apples to apples between states and counties here in with a mistake. 

Thom Canalichio:

Dr Ostrosky, with the questions about the asymptomatic cases and pre symptomatic phase, how does that connect up to our best recommendations for testing and when someone should get tested in order to make sure that their results are the most accurate as possible?

Dr. Luis Ostrosky:

So, the one thing everybody agrees on is if you have symptoms you need to be tested. And again, we ask people who have a very low threshold as to what we considered corona virus symptoms because we have anything from a headache to diarrhoea to a sore throat, to full-fledged fever and shortness of breath. So, in this day and age, if you're having anything that's remotely abnormal from your baseline, any new cough, any worsening cough, any different nasal congestion than you normally have. I would recommend you get tested for corona virus because it could be an actual infection.

Where people disagree is really what to do after somebody is exposed to Coronavirus. And the reason we disagree is because once you're exposed, you actually have the whole 14-day incubation period to become positive. And yes, most likely you're going to be becoming positive within four to seven days, which is kind of the 95% for the majority people. But there's some people that are going to be doing that earlier, and some people that are going to be doing that later. And so, sort of the knee jerk reaction once you hear you've been exposed is – I'm going to go ahead and get tested. And you actually maybe testing too early to detect the virus and creating a false sense of security that you're okay, when you still need to be sort of quarantined for the 14 days.

So, we generally recommend people to get tested when symptomatic and after an exposure if it's important to you to be able to sort of go back to work or go back to school, we want you to wait at least five days from the day of exposure to do testing. 

Thom Canalichio:

Great, thank you, Dr. Ostrosky. We have a question from someone in our audience, not a reporter but a health provider and someone who's on a school opening Task Force. Her name is Ella, thank you for your question in the chat Ella - are asymptomatic children, potentially disease conferring? I don't know whether or not we know this, but Dr. Dutch, do you have any thoughts about that? 

Rebecca Dutch:

Again, this is an area of ongoing research suggests that children who have an infection are generating infectious particles, so that they are able to - and it would make sense if they're infected, they have viral particles near the airway. Given that it would see most likely they could be infectious. I don't believe I've seen a study that actually looked at transmission between children so the answer is most likely yes, the only thing that's interesting is there were a few reports that I read out of Europe in particular that didn't see a huge change in spread rates with or without school closings, which would suggest that maybe children are not the massive incubators of virus transmission for this that they may be for some others - for instance, we know with influenza children are our major source of the spread of this virus. They just spread it like wildfire and take it home. It's not as clear that's the case for the Coronavirus. But again, we're really in the infancy and in figuring that out. 

Thom Canalichio:

Still a big unknown Dr. Ostrosky would you add anything to that? 

Dr. Luis Ostrosky:

Yeah, I think the way we approach children currently is, we think they're no more or less likely to be infectious than an adult - that can get as easily affected as an adult. They're not going to be spreading it more than an adult either. And what we do know in children is that they seem to fortunately get through milder forms of the disease, although there are some very severe forms in children. So, this is all playing into this very difficult equations as to when to bring back kids to school.

Thom Canalichio:

Something that occurs to me, Dr Ostrosky is if, younger children are carrying the virus but they're asymptomatic, they're therefore less likely to cough and sneeze, is that potentially a factor in reducing at least that, that they might be transmitting it? 

Dr. Luis Ostrosky:

Again, it's no more or less likely than an adult acting the same way. So, I don't I don't think we need to carve out children as special populations 

Rebecca Dutch:

And children like to yell- so that probably offsets some of the not coughing and sneezing. 

Thom Canalichio:

Yeah, absolutely. We have another question from Tina at Science 麻豆传媒, Tina, go ahead. 

Tina:

Um, so this question is Sort of about the justification for carrying masks. So, the WHO still doesn't recommend universal mask wearing and they've been reluctant to say that the corona virus is airborne. But the possibility of aerosol transmission is cited as one of the reasons for wearing masks. So, what's the evidence for and against aerosol transmission? And is that the important factor for why people should wear masks? Or is it the asymptomatic or pre symptomatic transmission possibility or is it combination of both? 

Thom Canalichio:

Dr. Ostrosky Do you have thoughts about that? 

Dr. Luis Ostrosky:

I have a lot of thoughts about that, unquestionably, masks are a game changer. I mean, we've seen it in our hospital. Before we started universal masking, we had a lot of transmission with between staff, between patients and staff, etc. The moment we implemented universal masking, that all went away, it was very, very clear we went to a pattern where now most of the transmission we see in the hospital is between staff members that take off the mask to eat together. And then there's a lot of research out there looking at masking in the community settings, showing a significant decrease in transmission. There's a lot of now really good case reports for you know, masking, for example, the one that came out in the MNWR today. This salon where two stylists were sick with COVID - they were wearing masks, and none of the clients got the disease. So, in my opinion, there's really no controversy as to whether mask help decrease the transmission of this virus, and it's only a matter of time before WHO catches up to this. I don't know if you want to say something about that Dr. Dutch before we address airborne or aerosol. 

Rebecca Dutch:

I completely agree, the data is very strong that masks matter. There was an epidemiology paper published about a month ago that really went back and looked at Italy and New York, and looked at what their transmission curves were and then put in the time point of when there was mandatory mask wearing put in place and you can see a shift in the curve in both places of by four or five days after that date, which would fit with the idea that when we all start to put masks on, we decrease transmission. Are we decreasing it to a 100%? No. But what I always say to people who are not so fond of this - oh, it's not perfect. Oh, we don't know - is if you are about to go in a room and people were going to shoot at you, and you had the option to put something on, that some data suggests is going to protect you 90% of the time, would you do it? And the answer would be yes.

Same thing is if you were - for your loved one -would you have them do it? Yes. So, this is again a choice that has good scientific evidence to suggest it will really make a difference and no scientific evidence to suggest it's causing problems. I don't particularly like wearing a mask, I'm not a huge fan of seat belts, but I wear them every single time I get in the car. They’re uncomfortable, but I wear them and it's the same kind of thing.

 Thom Canalichio:

Dr. Ostrosky did you want to also comment on the question of airborne transmission? 

Dr. Luis Ostrosky:

Perfect. So, we're in the midst of a huge academic debate of airborne versus droplet. So just to set the point here, what we think of airborne in infection control and Epidemiology are things that are suspended in the are and can travel long distances. So, for example, if you had an auditorium where there's somebody with measles or chicken pox or TB, the particles would disperse all over the auditorium and you would have almost anybody who's susceptible be infected. That's what we call airborne in infection control.

Then there's droplets - droplets are bigger particles that usually are pulled down by gravity, they have a trajectory, and they can travel at the most a meter or three feet. So, the current thinking is that this virus is primarily transmitted by droplets. They have large amounts of viral particles, and perhaps there is some inoculum that's needed to infect somebody. And then we have a new generation of engineers and scientists that sort of started to do experiments and they found that they could aerosolize the virus and you can detect RNA in these aerosols and the conclusion is that, oh my god, we have an airborne thing here, and when we actually don't know if this aerosols, again, can produce infected particles - we can detect RNA for sure. But we don't know if we can grow virus from these aerosols. And these aerosols aren't really going to be floating around the air, they can linger around, but they're not really sort of expanding and being viable like we would see with other diseases.

So, the debate right now is if this virus is airborne or aerosol mediated and the answer to that is probably somewhere in between. The primary route is going to still be droplets, but we do know that you can have some aerosols that may linger around the patient, for a patient that's positive. And they may linger a little longer than you would in a very close space with poor ventilation. So that's the current thinking. There's a letter that got written to the WHO and CDC by a group of scientists requesting that CDC and WHO acknowledge this is airborne, and WHO responded with - we read your letter, and we think there may be a role for aerosols, but the reality is we don't think this is airborne in the sense of what we call airborne things in epidemiology. 

Thom Canalichio:

So is it is it correct to say then, Dr. Ostrosky that the virus must be suspended in some form of liquid when it comes out of an infected person's mouth, it can't just - the virus can't just by itself survive in the air. 

Dr. Luis Ostrosky:

So, I'm going to let Dr. Dutch – as she’s a virologist.

Rebecca Dutch:

So, again, I wish I could give you an absolutely firm idea but what we think is that most viruses that are coming out like this are more stable if they're on these droplets. So, Corona viruses are these tiny things and they have a lipid membrane around them - kind of think like a - what you think of with an oil, coating the genome. That's not all that stable out there, but if you have a number of them put together and they're put together with some of our respiratory secretions, it provides more stability as they move out. And that's true for most viruses – Most - many viruses, particularly respiratory aren't that stable when they're outside of cells.

So, the thinking is that most of them are on these kinds of droplets. Could I promise you that there's not a single case of a viral particle out there and all - there probably is, but where are the majority?

So, I think that Dr. Ostrosky is completely right with what he was talking about - most of what we think is going on as these droplets, that's why six feet came up as an idea. That's why masking comes up as an idea. Is it possible that there's some aerosolized virus? Yes. As you probably hear from both of us, none of these things are simple to say this is exactly all the cases. And this never happens. What we're saying is this is probably most the time and occasionally you have some of this. But we don't have any reports that I've seen of virus, for instance, spreading through air conditioning systems and in apartment buildings, or spreading to the office four doors down even though you didn't see the person. The examples that are brought forward to suggest airborne are all things like a restaurant where the tables were further than six feet, but people were sitting in there for a long time, and one part of that restaurant more people got sick, things like that. I think it is worth looking more carefully at ventilation. I know when we're looking at how we properly deal with- I certainly think looking and making sure you're well ventilated is a good idea. It's also why being outdoors is likely much safer. You simply don't have some of the issues you might have indoors. But I think we still have to stick with as much as possible stopping all the short term spread that we know is going on and then starting to look at is there a small percentage that's this long return aerosolation? And if so, how do we reduce it? 

Thom Canalichio:

We have a question from Helene Bednarsh she’s a freelancer, she’s asking about the report that came out today citing presence of a rash in the mouth or potentially on the skin as an indicator of infection. I wonder if Dr. Dutch or Dr. Ostrosky you know anything about that? 

Dr. Dutch:

Oh, we certainly get a lot of interesting symptoms with this virus, its not impossible that this could be there – I haven’t seen the report yet. Certainly within the nasal cavity and mouth we get some things that are more unusual to this, one is a loss of taste and smell, someone I know recently had this – a complete loss of the ability to taste or smell for 10 days, so you're certainly getting active replication up in the nasal epithelium, in areas of the mouth that could generate some kind of rash, I haven’t heard of this though as a common symptom. 

Thom Canalichio:

Dr. Ostrosky any knowledge about reports of an oral rash? 

Dr. Ostrosky:

No, we’re still finding more and more reports of a typical manifestation of Covid, like this, like skin nodules and the reality is that this virus is going to become so prevalent that you're going to see this virus with other things, right – with other illnesses and that’s where it gets really tricky epidemiologically to see if this is a finding of Covid or with Covid. So, looking forward to see more data on this, but in any case it would be an a-typical and rare symptom that we see. 

Thom Canalichio:

Another question from Tina at Science 麻豆传媒. Tina go ahead. 

Tina:

I was wondering is there data to tell us what actually an infectious dose of the coronavirus is at this point? 

Dr. Dutch:

No. for most viruses its quite a bit more than one, but as you can anticipate that’s a really difficult experiment to do. First of all, I assume what we really want is an infectious doze in a human – we can’t do those experiments so they're I'm sure looking with animal models. There is several good animals’ models that have now been developed to try to start to determine that but I haven’t seen a published paper that really carefully looked at that. 

Thom Canalichio:

Dr. Ostrosky any thoughts on that question? 

Dr. Ostrosky:

Yeah again we are barely having any quantitative assays for this virus at this point, so first we need to develop the technology for quantitative exposures and as Dr. Dutch said it would be unethical to purposely infect people, but then I see experimental designs where you can work around a hospital and see what the doses are and you can have many people that are infected in an area or another etc, so – more to come on that, but I do believe there could be an inoculum effect here – going back to Emiliano’s question about who is going to get sicker – we think there is probably generic determinants as to your immune response to the virus that are probably going to explain why some people don’t get anything and some people land up in the ICU with wide lungs and another explanation could be really the doze, the infected doze or inoculum and I do feel that anecdotally people that have very large exposures are more likely to get the disease. 

Thom Canalichio:

That’s a great question and it seems like we’ve had a couple of other questions in the chat get answered in the course of answering that question both from Kids Community Dental Clinic – one of our attendees asking similarly the more virus you're exposed to – does it mean the worse the disease effects are – do you know anything about prolonged exposure in a small space say within the same household, does that potentially result in the next person infected getting a more severe case or is it still just so variable from patient to patient that that cant be traced with good control? 

Dr. Ostrosky:

It’s really fascinating, to study the cases we’re seeing because I’ve had families where one member has it and the whole family gets it, 6-7 members get it and they're all in the ICU, super sick and that happens and then I’ve had cases where I have one patient that has the illness and he doesn’t isolate himself from his wife, they're still sleeping in the same bed, sharing meals etc and the wife never gets it and we know she never gets it because they're both physicians and they're both getting tested repeatedly and one of them never gets it. So, we still need to learn a lot about this virus. 

Thom Canalichio:

From the chat on the topic of the earlier question about oral rash, a very helpful comment from Raquel – she chatted a link to an article comparing the lesion to similar to herpes simplex virus and that is in the chat if anyone is interested in exploring that particular idiosyncratic symptom further. Also, Benita from WNY Albany asked further about the person to person variants in the load of virus or the severity of disease.

I would love to mention one study that I familiar with that is coming out in about a week from one of our members, the Sbarro Health Research Organisation based at Temple University in Philadelphia, Dr. Antonio Giordano there, they have studied the HLA gene and taken data from Italy, now that its been significant time since their peak of disease and they studied variances in the different alleles of the HLA gene system and may have identified particular ones that may indicate worse or less bad spread – that should hopefully be coming out in the next week or so, if anyone is interested in that you can contact me and I’ll connect you with them about that, I just happen to be consulting with them about their release about that.

Dr. Dutch I’d like to ask you kind of about these asymptomatic patients potentially still having actual symptoms that they might not be aware of, is this something that can be seen on a chest scan for example – changes to the lungs that they may not realise have happened. 

Dr. Dutch:

I will tell you right now this is primarily anecdotal from things that I’ve heard, I’d also love for Dr. Ostrosky to comment on this – but I’ve certainly heard a few reports from people that they had someone who didn’t realise they had it, they come in, they're antibody positive and they actually have lung symptoms that look like they’ve been infected, or a patient showing up to the ER who don’t really think they're sick but they actually have lower pulse ox readings and they shouldn’t have felt fine but they seemed to. So those are all kind of worrisome symptoms, meaning people are actually ill, just somehow its crept up on them and they haven’t identified it as being a real problem. 

Thom Canalichio:

Dr. Ostrosky any thoughts about that or further comments? 

Dr. Ostrosky:

Yeah so we have very interesting patterns as well, again the situation where somebody is working around – they feel fine and you put on a pulse oximeter on them and they're scoring less than 90 and they're feeling fine, that’s what we call silent hyperoxemia and its something that we’re looking at, particularly in younger people that can tolerate hyperoxemia better and then the other thing is we have noticed it in our trauma service, we have people that have been through car accidents, they have strokes, real brain bleeds etc and then in the workup they get a cat scan of the chest and wow! We found the classic signs of Covid there – so its really interesting to know that there could be such level of infection without clear signs of the symptoms in the presentation. 

Thom Canalichio:

I’d like to go to Charlotte for a question on blood types. 

Charlotte Libov:

Yeah, thank you. There seems to be a pretty much of an agreement on early reports that blood type mattered, that people of type A were more likely to get infected and then in the last day or so I think there was a pair of studies that came down saying that this really isn’t possibly the case – I know early research is really research but do you have any views on this? 

Dr. Dutch:

You're exactly right, research is research and I try to always stress to my students – including the ones that I teach that science is people learning and that’s why the story changes – I teach virology, its different every year because we learn new stuff. So, there are several reports that suggest that this linkage is there, there were early reports out of china that suggest that patients with type A blood had more highly representation in the patient population than you would expect and those who had type O were under represented. The other report that suggested this was important was called a GWAS study - Genome wide association study that came out in Italy relatively recently and they found two areas of the genome that seemed to link with increased infection rates and one was the area around where the blood type that genes were – there are however some other genes in that region and it remains possible that its not actually the A thing, its something related in the genome that was having an effect. Now I haven’t seen the report you talked about today, in all of those studies, it wasn’t an all or nothing. It’s not something where I would say – I'm type A, my cousins type O – you have to go to the grocery store cause you're safe and I can’t go cause I'm in danger. It just elevates your risk. Just like being slightly older elevates risk, other things elevate risk, so I think its one that we’ll have to keep teasing out the story. 

Tom Canalichio:

Dr. Ostrosky anything you’d add to that? 

Dr. Ostrosky:

No, this started as an epidemiological observation in china and then the Italian study really brought us granularity as to what genes are emboldened and they do show in my opinion a clear association of severe forms with Type A and a protection for Type O, its not really the blood type its sort of what the genes are, as Dr. Dutch was explaining and the concentration of these genes in those blood types but I think more to come on this story. 

Tom Canalichio:

I’d like to ask about one other recent news development and then we’ll work towards a close, I know Dr. Ostrosky you have a hard out in about five minutes so I want to make sure to get you where you need to go. Reports in the last few days about changes to hospitals and where they're reporting case info, switching that to go to a more centralised database at the department of health and human services in Washington rather than directly to the centres for disease control. Dr. Ostrosky is this a sign for concern at all or what are the pros and cons of making a change to the reporting mechanism here for the hospitals? 

Dr. Ostrosky:

So, I'm going to start off by saying that I'm maybe naïve but I see this in the field, the way we started to report Covid data to the government was through an existing system called the NHSN that we used for reporting associated infections. There was no system to report Covid to health and human services or CDC, they sort of created a new module for NHSN and that’s how we’ve been reporting Covid but it was kind of – what I would say it was a generic system, it wasn’t assigned to do that and now they’ve rolled out a specific system to directly report the cases to HHS. Of course people are weary about this, there's still a bit of mistrust, I see it really as a more direct route of data to where it needs to go, for a big decision making and nobody is saying that CDC is going to be excluded from seeing this data or from looking at it, so I'm maybe a lone voice here but I'm not too concerned about this. 

Thom Canalichio:

I think that’s very reasonable and somewhat reassuring Dr. Ostrosky but certainly a lot of people may be sceptical or suspicious with the regular contradictory or inconsistent messaging from some public officials and so Dr. Dutch I want to ask you if there was any evidence of data being suppressed or anything – how would we know and what would reassume people about this?

Dr. Dutch:

So, I think – first to answer the first question – my concern – what we want is transparent and available data and as long as this new reporting system generates that, then this is great and there have been complications – from what I can tell and Dr. Ostrosky would know much more than me – with the CDC system and it has not seemed to work incredibly well some of the time. What will matter is whether now data flowing in is readily accessible to the CDC, to other units that are looking for this data, that’s how we’ll know – if we have problems with people who are doing modelling, accessing the data they need to do the modelling, then we’ll know that you're not getting access. If we’re instead giving – those people who are readily being able to access the data, given the data and the data is complete and appears to be hopefully an improvement on what we had, then we’ll know the system was working, I think we’re going to have to look and see. 

Thom Canalichio:

Thank you, Dr. Dutch, with that we’ll get drawn to a close. I want to do a quick plug, we’re going to do another one of these next week, possibly actually two of these next week so please stay tuned for information about those, one will be focusing on cases of Covid among cancer patients, and we’re also convening a panel to talk about the debate and controversy about mask ordinances and what are the objections, what’s the science about that- so we had some questions earlier about the effectiveness of masks, I’d encourage you to join us next week to discuss that further. With that I will say thank you to Dr. Dutch and Dr. Ostrosky – for any media who are on the call we will make sure to get you a video and transcript. If you're not on the registration list send us an email to [email protected] and we’ll be certain to get you that information once available. With that I will say stay safe, stay healthy and good luck. Thank you very much everyone.