Coronavirus (COVID-19): Press Conference with Stephen Kissler, 10/14/20

You’re listening to a press conference from the Harvard T.H. Chan School of Public Health with Stephen Kissler, research fellow in the Department of Immunology and Infectious Diseases. This call was recorded at 11:30 a.m. Eastern Time on Wednesday, October 14th.


MODERATOR: Dr. Kissler, do you have any opening remarks?

STEPHEN KISSLER: No, just that we seem to be, again, transitioning into a period when we’re seeing lots of cases rising across the country. So it’s a lot of talk about second waves, both here in the U.S. and around the world, to which I think is apt and something that we ought to start preparing for. So I’d be happy to talk about that and anything else that anyone’s interested in. I think I’ll leave it to the people who are here.

MODERATOR: All right. Looks like we have a few questions already. First question.

Q: Trying to unmute myself, hello, can you hear me?

STEPHEN KISSLER: Yes, I can hear you fine.

Q: The city of Brockton is reaching 5000 confirmed cases of coronavirus, making it one of the most heavily hit cities per capita in the Commonwealth of Massachusetts. The city, about a hundred thousand people, given the limited availability of testing early on in the pandemic and the results of antibody studies done in some places. Do you think it’s possible that our city, Brocton, has a much higher undetected rate of COVID-19? And if so, how much bigger could that amount of undetected cases be? Could the actual amount be closer to twenty percent than the five percent we know about?

STEPHEN KISSLER: Yes. So it could be. You rightly pointed out that early in the pandemic we didn’t have a lot of testing capacity, so there were a lot of cases that we missed then. And so I would imagine that as Massachusetts was seeing a lot of its transmission earlier this spring, there were probably a lot of undetected cases in in Brockton as well as across Massachusetts and across the country as well. I think one place that I could look for information about this is New York City. And so one thing that we know for sure is that different neighborhoods in New York City were affected very differently. We know that both from the virological testing and from the serological studies. And it looks like according to our best estimates, some of the neighborhoods that were hit hardest probably have on the order of potentially up to 50 or 60 percent of the cumulative number of people who have been infected. And most of the city is much lower than that, more on the order of 10 to maybe 20 percent. And so I think that if we sort of map New York City back onto Massachusetts for a community that has seen a major outbreak, as you’re saying, like Brockton has, it seems to me that sort of drawing parallels from New York City that we could very well be on the order of 10 to 20 percent of people who have been exposed and infected with the virus. So I think that that’s a reasonable estimate.

MODERATOR: Do you have a follow up?

Q: Yes. One quick follow up. This rate of infection, say 10 to 20 percent. Could this rate of infection provide any level of herd immunity for the city?

STEPHEN KISSLER: It could slow down transmission somewhat. But according to all of the best estimates that I have available, that’s still far too few to actually achieve herd immunity in the sense of preventing major outbreaks from happening. Again, as we’ve seen in New York City, there are communities who have seen transmission on the order of 60 percent. That suggests that those communities shot past that 10 to 20 percent substantially. So I think that herd immunity threshold of 10 to 20 percent is probably too low. It seems like in all but the very hardest hit communities in the country, there’s still plenty of susceptible people around to sustain further outbreaks coming into the fall and winter.

MODERATOR: Are you all set?

Q: Yes, I’ll let other people ask questions if I have time for another one, I’ll ask later. Thank you.


MODERATOR: Next question.

Q: Hi, thanks for taking my question. You mentioned at the beginning that it’s looking like cases are maybe starting to build again, to increase again. And I guess I wonder what’s similar or different from this time compared to either the spring surge or the summer one in the south?

STEPHEN KISSLER: Yes. So I’ll say a couple of things. So first, the spread of COVID around the country roughly follows the order of population density. So a major outbreak in New York City first and then we saw big outbreaks in Florida and Texas. California has sort of been sustained over much of the pandemic. And now we’re seeing it sort of spread up into the Midwestern part of the US. So I think part of the story, what we’re seeing relative to the spring is that we’re just sort of seeing the transmission sort of trickle from major population hubs into other parts of the country. And so that’s one of the distinguishing factors is that many of the communities that are getting hit now are not the ones that were hit earlier in the spring. If you aggregate across the country, it looks like we’re rising again. But there’s a lot of geographic variation in there that shows that the pandemic really has been sort of spatially moving. Now, that said, there are many communities who are seeing rises in transmission, even though they saw major outbreaks in the spring as well.

So I think a couple of things to note about that. One is that due to increased testing, we are able to detect a lot more cases and we’re able to see these increases a lot sooner than we were able to see earlier in the spring. So as we’re starting to see rises in cases and some places are seeing case levels that are matching or surpassing what they saw in the spring, doesn’t necessarily mean that the prevalence of infection is actually higher than what it was in the spring or even completely comparable just because of the increase in testing. Now, the fact that we’re doing more testing, I think the best thing about that is that we’re able to detect these rises sooner. So these sorts of things may have been happening over the course of the year already, but our ability to detect them is enhanced because we’re doing more testing. And that’s a very good thing because we can stay on top of cases a little bit better. So I think that’s another of this story as we’re seeing cases rise. The last thing, though, is that it seems like as the pandemic has gone on, there’s really been a story of shifting age groups and demographic groups who have been hardest hit and most affected by the spread of the virus. And so over the summer, and to my knowledge up until now as well, sort of shifted from really seeing a lot of concentrated outbreaks in nursing homes and older populations into seeing more transmission among especially young adults.

I think that’s something that we can probably expect to see going forward as well with potentially even a shift in the age distribution even lower as students in schools begin to have outbreaks as well. In a way, that’s a good thing because the younger people are less susceptible to severe outcomes of infection. But, of course, infection spreads. So ultimately, what that will mean is that there will probably be a longer delay between the observed cases and, for example, hospitalizations and deaths, because there have to be a couple extra chains of transmission between the people who are first getting infected and then getting the disease passed onto the people who are going to be most strongly affected. So all of those things are in play. But just to summarize, doing more testing, so detecting rises earlier, the age distributions are shifting, which can lead to a longer delay between observed cases and severe outcomes. And the prevalence of cases sort of looks higher now than it was in the spring, even though it not necessarily is. And then there’s sort of the geographic shifts as well.

Q: I think that was really helpful. Thank you. I guess one follow up. I follow you totally on the geographic differences over time. And I don’t know if it’s too soon yet, but here in Massachusetts, also New York, there’s evidence that things are maybe starting to slowly increase. Like maybe they’ll be able to be suppressed, and it seems like these would be some of the first places where there would be a true second spike in cases. Is that generally right? What does that reflect in terms of the epidemiology of this?

STEPHEN KISSLER: Yeah, it’s tricky because I think that the things that drove transmission in the spring are not necessarily the same ones that will drive it in the fall. So we can look to the example of flu pandemics in history as well, where, for example, in 2009 and also in 1918, there was this early wave of transmission in New York City. And then in the fall and winter, we saw sort of transmission that spread around the country. Then in 2009 in particular, the places where transmission got started, that was actually driven largely by the opening of schools. And it seems like there is this interaction between schools and weather patterns that sort of led to the geographic ordering of outbreaks going forward. So when essentially everyone in the population was susceptible, I think the population density was a huge factor. Population density will continue to be. But also, many of the places that got hit hardest have people who went through a very bad experience this spring and so are going to be a lot more cautious going into the fall as well. So there’s sort of these competing factors contributing to the spread of the virus. So I don’t think it’s necessarily the case that the places that were hit earliest in the spring will also be hit earliest, hardest in the fall and winter. I think there may just be different sort of different epidemiological dynamics in play there. And I expect schools may well play an important role here.

Q: Thanks so much.


MODERATOR: Next question.

Q: Hey, Dr. Kissler, thanks for taking my question. Nice to speak to you again. I have two separate questions. I’ll try to keep them brief. The first ones about in-person voting, actually, I don’t know if you’ve looked at this at all, but I’m doing a story on, you know, what precautions the local election supervisors are taking in the safety of in-person voting. And just give you a sentence, masks will be required to enter. There’s going to be a lot of sanitizing. The poll workers and election staff will be wearing face masks and shields and they’re trying to move people in and out pretty quickly. I did ask about ventilation. The AC is going to be on and they’re going to keep the doors open to try and create some ventilation. But I’m just curious to get your thoughts about what you would pay attention to with the safety of in-person voting, what might be risky and what might not be.

STEPHEN KISSLER: Yeah. So first off, it sounds like they’re taking all reasonable precautions. Those are absolutely the things that I would recommend if I were asked to advise on keeping a polling station safe in terms of COVID. So that’s really encouraging. So the way that I often think about it, as you likely have as well, is just in terms of relative risk. So thinking about what other activities we partake in, that might carry a similar burden of risk as voting. And with these particular precautions in place, it seems to me like this would be similar to going grocery shopping or going into a restaurant and picking up a takeout order but having to wait for that order to be to come up. And both of these things are considered not zero risk, but relatively low risk in the spectrum of things that we can do with respect to COVID. So I think that it sounds pretty reasonable and it sounds like it’s well within the parameters of acceptable risk that we’ve sort of adopted as a society up to this point. And of course, voting is an essential civic activity. So I think that making it as safe as going to the grocery store is probably a good target to shoot for. And it seems like these precautions are doing roughly that.

Q: Thank you. So just one other question unrelated to voting and then I’m done. Just on the topic of school safety and school reopening’s, our education report has been doing an amazing job following the situation here in Miami. And she wanted me to relay questions to you about ventilation and schools here in Miami. We have a lot of schools that are designed to keep the windows closed during the school year because of air conditioning. So there’s a lot of questions about whether that’s something that should be addressed in every school. Some schools have better ventilation. Some have installed these MERS 13 filters. And, you know, they’re installing these filters in their H vac systems, but not all of them have done that. So I just want to get your kind of general thoughts on ventilation and what’s necessary when students are wearing masks and at least somewhat physically distance, how much you should be concerned about ventilation?

STEPHEN KISSLER: So anytime people are spending prolonged periods of time indoors, together, I think ventilation is an essential thing to pay attention to, I would say. And by long periods of time, I mean like on the order of an hour or more in a single space. But that said, I think there are a lot of things that one can do to improve ventilation that don’t require overhauling an entire building’s H vac system. With many schools in Florida the architecture can be different, where sometimes the classrooms open up to the outdoors or something. So if you can open up a door and vent the air outside or even into a hallway or something like that, just as much as you can to get the air from places where people are congregating in high density to mix with the air in places where people are in low density so that you can just sort of reduce the concentration of virus is important. And the filters can be effective as well. I think actually one of the best sources of information that I’ve seen about that is a previous media call, one of these same calls by Joseph Allen from, I think a month and a half ago or so, speaking about the tradeoffs between number of air exchanges within a room and how you can sort of balance that with filtration and what’s necessary there. There are actually even some spreadsheets online that I think Professor Allen and others have been involved in producing that sort of allow you to put in parameters of your indoor space and determine sort of what a safe setup would be with relatively few resources. So I would potentially direct you to that. But I think the most important thing to underline here is just that if you do have people congregating in indoor spaces, no matter how much distancing is happening, if they’re going to be there for an hour or so, ventilation becomes really important because that’s where the aerosol transmission becomes especially important because virus accumulates in the air.

Q: Thank you so much for your time, I appreciate it.


MODERATOR: And I’m putting in a link to some of Dr. Allen’s resources, putting that into the zoom chat. I believe there is something like a spreadsheet that Dr. Kissler was referring to, where you can put in ventilation and what you have and what they recommend you do. So I’ll try and find them, put them in the chat as well.

STEPHEN KISSLER: Awesome. Thanks, Nicole.

MODERATOR: Sure. Next question.

Q: Yes, hi, thanks for taking our questions. I also want to ask about schools. I guess my first question is, I know we’re only, depending upon the state, a month or two into the school year. But what do you think about the number of cases in schools so far? Is it encouraging or discouraging? Is there any takeaways from school reopening so far?

STEPHEN KISSLER: Yes, there have absolutely been outbreaks in schools. But I will say that I’ve been encouraged by the fact that they haven’t been more widespread than they have been. I actually expected there to be more large outbreaks in schools than I have so far become aware of. So I think that’s good. And I think that that’s a testament really to the preparation of administrators and the hard work of teachers and from students, that sort of thing. All really important. And I know that many schools have been adopting different strategies and some of them are more based on ventilations. Some are more based on having plexiglass barriers or something more based on masks and taking breaks outdoors and these sorts of things. But the most important thing is that everybody’s doing something. And I think it gets back to this idea that the non-pharmaceutical precautions that we can take against COVID are in some sense additive. And so we don’t necessarily need to do everything. But as long as we’re doing a couple of things which most schools seem to be doing, that can do a really good job of reducing the spread of COVID. I don’t want to prematurely declare the reopening of schools a rousing success. But I do think that they have seen more success, certainly, than I expected. Even though I tend to run on the side of pessimistic a little bit. But, yeah, I’ve been modestly encouraged by how schools have fared so far. So there still be definitely difficulties going into the winter. Again, as behavior changes and people need to congregate indoors a little bit more. And as fatigue for some of these precautions starts to come in. So I think we’ll have to just make sure we stay vigilant. But it seems like what people are doing so far is, by and large, working OK.

Q: OK, just a point of clarification and then a follow up question. Is there any way to tell if the rate of transmission or virus prevalence in schools has been lower than in the society as a whole or about the same?

STEPHEN KISSLER: You know, I don’t actually know that. I would have to look up statistics, so I’m sorry. I can’t speak to that, exactly.

Q: OK, then my follow up question is, what do you think so far about the robustness of the data that states are providing around schools? Maine just started doing a school by school, update cases. And I know a few other states are doing that. Are a lot of states doing this or not that many or do you have a sense of that?

STEPHEN KISSLER: So I don’t know of many states that are doing a school by school breakdown at the moment. I think it can be a valuable thing to have for sure, although it takes a lot of resources. The most important thing here, actually, is that beyond even making those data available is making sure that you’re doing enough testing to make those data reliable. I think that one of the most important additional things that we can do, especially for primary and secondary schools, that isn’t being done at the level that I would hope right now is improve testing and make sure that ideally students, but especially people in the higher risk groups, which will probably tend to be teachers and administrators, are being tested regularly. So that will help us make sure that the cases that we do report from schools are actually an authentic representation of what’s happening within those schools. So I think both of those things are important. But I’d actually say that doing the testing itself is probably the first priority. And then making those data sort of available at a very granular level is something that can probably follow. Otherwise, the data is not necessarily all that useful.

Q: Thanks. Just to make sure I understand a point that you made. Are you saying that there’s not many states right now that are providing school by school data? Is that what you said? I just want to double check.

STEPHEN KISSLER: To my knowledge, that’s correct. But it’s been a couple of weeks since I’ve looked. So I don’t know if I’m fully up to date.

Q: Great. Thank you very much.


MODERATOR: Next question.

Q: Hi, thanks for taking my question. You mentioned cases are building again, and of course, we’re heading into the winter. Colleges that are open for in-person instruction this fall are also nearing a point in the semester where they’re beginning to think about sending students home for winter break, which for a lot of schools is supposed to start around Thanksgiving? I’m curious if you can share what are some considerations of public health practices colleges should be thinking about in order to send students home safely. And are there any scenarios in which they should not send students home?

STEPHEN KISSLER: Yeah, thanks. This is a really tricky challenge that’s facing colleges and universities right now. A couple of things. So for now, we do know that the mixing, the interpersonal mixing that happens during the winter holidays, it does seem to contribute to spikes in respiratory illnesses in non-pandemic years. You can pull out a signal from just regular flu transmission. Some of that might be driven by physicians seeking behavior and so on. But nevertheless, it seems pretty consistent that as people go home and congregate with different people who they haven’t seen for a while, that can lead to the transmission of disease. And that will, of course, be true for COVID as well. So this will be really important to do this carefully. I think that one of the again, related to the previous question, one of the most important things that we can do is make sure that to the extent that we’re able to do that, the students who are going back home are not actively infected with COVID, and so that requires consistent testing, which many colleges and universities are doing. And what I would hope as well is for the colleges and universities to work with the students to accommodate their home situation. And so one of the things that I’m concerned most about is, going back to a previous question when I was talking about the age distribution of cases, if we can keep cases sort of concentrated in younger age groups who are at low risk of severe infection. That’s better than allowing it to spread through older populations of populations with more comorbidities.

So one of my biggest concerns with sending students home in the fall and in the winter is students who are living in multigenerational households and students who are living with parents, relatives who have high rates of comorbidities. So my hope is that colleges and universities would be able to do two things. First of all, to be able to accommodate, really providing those students with other places to stay, if they so choose over the holiday so that they don’t put their families at risk, if that’s something that they’re concerned about. That’s a very tall ask. But epidemiologically speaking, that’s something that I would hope for. And then the other thing is that colleges and universities, I think, have an opportunity to share good public health messaging with communities that don’t necessarily have direct access to the sort of education that happens in colleges and universities. So I think that making sure that students are prepared with the information that will both keep themselves and their families safe, that they can share with their families when they return home is another way that they can help prevent the spread of disease once they’re there. So I think that sort of public health messaging might actually be one of the most important things that we can do, as well as maintaining testing to the extent that we’re able.

MODERATOR: Do you have a follow up?

Q: No, thank you.


MODERATOR: Next question.

Q: Hi, Dr. Kissler. Thanks for your time here today. Yes, to get back to the concept of measuring whether the pandemic is getting better or worse. We’ve talked about the challenge with using case level data. We’re testing more people, so generally, there might be more stuff to find. Might not. And you look at positivity rate and you’re trying to figure out what are the odds. I’m wondering if you found a good metric that you go to that you say, OK, if this is the one that I’m looking at to see whether it’s getting better or worse, this is what I use. And I raise that because some people have told me hospitalizations are the key for doing that, because generally people who got sick went to the hospital no matter how much testing was. But even with that, I have questions. So I’ll save that for the follow up. But I’m just curious kind of what you think of that conundrum.

STEPHEN KISSLER: Yeah, it’s tricky and it’s not a very satisfying answer. But in terms of asking whether cases are increasing, are getting worse, I generally look at, well, two things, sometimes three. So the positivity, I think, is really valuable because, again, it tells you, like you said, a rough sense of the proportion of people who are seeking testing who are actually infected. And so that’s a rough proxy for the prevalence of infection in the community. Very rough, but decent. And then also just the level of testing that’s happening as well. I’m only able to interpret the positivity if I also know what the trends and testing are. So if I’ve seen a huge spike in testing, like many states saw at the start of the school year, because schools were doing a lot of testing at colleges and universities, at least, that drove the positivity down in many places. But that probably didn’t actually reflect a decline in prevalence. It was just that you’re testing lots of people who aren’t infectious and aren’t infected. So it’s triangulating between those two things, both the wrong number of tests that are happening and the percent positivity and making sense of the two of those together is the best way that I’ve found so far to determine what’s happening sort of in real time with the epidemic. Now, of course, with hospitalizations and deaths, it’s because you’re seeing those severe infections. It can be a little bit more reliable than the round number of cases that we’re observing through testing. But, of course, those data are always delayed by some extent, and they’re also enriched for age groups, for older age groups and people with comorbidities. So that can sort of mask the sort of transmission that’s happening in the community in other less susceptible to severe infection age groups, which could lead to some important blind spots. Because if there is really infection raging in those communities, then there could be a crisis coming down the line. And if we’re only paying attention to hospitalizations, we’re going to miss that altogether and not be able to respond appropriately. So for me, it’s the number of tests and the positivity interpreted in tandem. That’s the most important.

Q: Just really quick in and I understand what you’re talking about with hospitalizations, which it sounds like what you’re saying is they have to be put in the right context and you’re going to be missing some stuff. I’m wondering within the hospitalizations, if you have a preference for admission data? This is a very in the weeds questions, I apologize. We have admissions data based on symptoms, CLI, they call it here. We also do bed counts. Same thing HHS does. And I’m wondering if there is a preference among those two, is symptom based viewed as better or if the bed counts, somebody testing positive redeemed to get a PUI is a better way to get a gauge on that part of this pandemic?

STEPHEN KISSLER: I’m not actually sure which I would choose. If you were to ask me in this moment, I would say that the admissions are useful, again because they’re probably a little bit timelier. And so if you start seeing rises in admissions, that gives you some important information about sort of what’s happening a little bit more currently. With the bed counts, potentially, that information is a little bit more reliable. I think the greatest value of that information is actually maybe even not so much to determine prevalence in the community, but to assess relative to the capacity of the hospitals how close we are to exceeding our health care resources. Which, of course, is one of the biggest concerns. So it really depends on what you’re trying to measure. If you’re trying to measure how much infection there is in the community, I might air on the side of admissions. But if you’re trying to measure our capacity to respond and sort of how much bandwidth we have for cases to continue increasing them, then the bed count might be a more valuable metric.

But you’re right. I’d have to look a little bit more closely at sort of trends in those statistics to see how they’ve fared over time, to see if one is more precise and accurate representation of what seems to be happening in the community. Now, as a quick follow up to that, I mentioned what’s happening in the community. The most effective way that I can tell that we know of to do that is through serological studies. And so we actually know how many people have been infected in the past. So using that, that can really help us triangulate what has happened in the past and then how our previous Real-Time statistics match up with that. But we’re still a long way off from doing those serological studies at a level of detail to really do those kinds of calculations reliably, unfortunately.

MODERATOR: Are you all set?

Q: We are all set. Thanks so much.


MODERATOR: Next question.

Q: Hi, thanks for taking the time. Can you talk a little bit about the seasonal effects on the virus, how much the anticipation of a fall surge is just based on cold weather bringing people indoors versus the actual effect of cold and humidity on the virus itself and its ability to spread?

STEPHEN KISSLER: It’s difficult to tease these apart, and it’s still an open question. As far as I can tell, it’s likely to be a combination of both. This is informed a little bit by what we know about the transmission of flu as well, but also from what we’ve seen about COVID transmission in the southern hemisphere. So seasonal coronavirus transmission peaks pretty reliably in the northern hemisphere sometime in December or January. And the timing of coronavirus outbreaks is a little bit more regular than the timing of seasonal flu outbreaks. So the flu season can sort of shift all the way from October, all the way through March or so, whereas the peak transmission of coronaviruses really seems to be largely concentrated in December and January. So what does that mean for us? Well, it still doesn’t necessarily help us tease apart whether weather factors or behavioral factors are more important for coronavirus transmission. But I think what that does suggest is that to the extent that SARS-CoV-2 follows the patterns of the other coronaviruses, we’re a little bit more likely to see these resurgences of infection a little bit later in the year than we might for flu, where, for example, in flu pandemics, we’ve seen in 1918, 2009, saw some really sharp rises of infections in starting even as early as August or in 1918, it was closer to October. But we may be starting to see that second surge now. I really expect transmission to increase sort of later in the year, probably November, December. And the reason I’m shifting that a little bit earlier than the December January is just because there are still so many susceptible people in the population that it’ll be easier for SARS-CoV-2 to spread than the seasonal coronaviruses, so it can sort of take off a little bit earlier. But that said, it’s still an open question as to what extent it’s climate factors versus behavioral factors that are driving this increase in cases. My guess is that at some level of both, probably the behavioral factors will be a little bit more important here. But I think that’s something that we’re only going to be able to tease out after we’ve seen at least one full year of spread across the world and SARS-CoV-2. Otherwise, we just don’t really have the statistical power to really make the inferences that we need to.

MODERATOR: Do you have a follow up?

Q: No, I’m good. Thank you.


MODERATOR: Next question.

Q: You mentioned climate as a factor and behavior as a factor. Isn’t there a third factor, the immunological angle, or would you include that under climate? My understanding is that seasonality is kind of a mystery, actually, nobody knows exactly why diseases are seasonal.

STEPHEN KISSLER: Yeah. And for some, it’s more of a mystery than others for sure. The seasonality of flu is sort of one of the canonical examples where we know a little bit, but we probably don’t understand everything about the seasonality. At this point, it’s pretty clear that absolute humidity contributes to sort of the ability of the flu virus to linger in the air. So colder, drier conditions just sort of enhance the ability of flu to spread to some extent. Now, whether that’s true for SARS-CoV-2 or not, we don’t know. But you also mentioned the immunological factors. So you’re right that that plays into this as well. And that also varies from disease to disease, from pathogen to pathogen. And importantly, for the seasonal coronaviruses, we see these annual outbreaks.

But there’s sort of this interesting interplay where the coronaviruses we have that circulate seasonally come in pairs that are genetically related to one another. These are the ones that cause the common cold and they sort of trade off years, it seems, where one year one of them will spike and then the other year the other one will spike. And essentially what’s happening is that there is an immunological factor where it seems like over time, the immunity to those seasonal coronavirus’s wanes, declines. And so what you end up with is the opportunity for the coronaviruses to spread because there’s enough susceptibility building up in the population or enough immunity lost in a population, sort of build up this pool of susceptible people for the viruses to spread. Now, I don’t know. There’s still a lot we don’t know about immunity to SARS-CoV-2. But I don’t anticipate that to be a substantial driver of the wintertime increase in cases that I’m expecting to see for SARS-CoV-2, partly because I anticipate that immunity to SARS-CoV-2 will probably on average last at least as long as it does for those seasonal coronaviruses. We don’t know for sure, but if that’s the case, then people who have been infected in the spring are likely going to have some level of protection going into the fall in winter. So I think for this first pandemic wave, probably the bigger factors are going to be behavior and climate to the extent that exists as a factor for coronavirus transmission. And then as we move forward and SARS-CoV-2 continues to circulate in the population, then I think it’s likely that it will actually become a seasonal wintertime virus. And then the interplay, the immunological interplay will sort of enter in as a third factor that contributes to it seasonality as well.

Q: So on climate, what do you think is the weather that the coronavirus prefers? Is it similar to the flu, like cold, dry air?

STEPHEN KISSLER: I would imagine so. And the reason for that, mechanistically speaking, is that both of the viruses spread through basically respiratory droplets. And here I’m using droplets is sort of a rough term that includes droplets and aerosols and everything, like bits of water that can hang in the air for various periods of time. And there’ve been experiments that are shown that those can sort of survive and spread a little bit easier in conditions that match up with the weather conditions that you see during the winter. So to the extent that the flu and coronaviruses spread through similar modes of transmission that have to do with sort of this evaporation rate of these droplets and aerosolization rates and these kinds of things, I expect them to share a set of climate factors. Now, the magnitude of that effect will probably differ between the two. But I expect the underlying drivers to still be the same.

Q: Thank you very much.

MODERATOR: Next question.

Q: Thank you so much for taking my question. I wanted to go back to something you said earlier on the call where you were talking about case rates in areas that had been hard hit in the first wave of the epidemic. There are some in the administration who are floating theories about the concept of herd immunity. And I’m curious. Look at New York. They’re having lower case rates now. So this works. But it sounds like what you’re saying is that it’s just people are very aware of the problems and take the necessary actions to make sure they don’t get infected.

STEPHEN KISSLER: Yes, that’s right. So I think that the clearest source of information on this is from serological studies. And it’s absolutely crystal clear that there are still enough susceptible people in the population, even in major parts of New York City, to sustain outbreaks. So I don’t see how herd immunity can be the explanation for why rates in these in these places remain low or have remained low for a while. If you do look at New York City, for example, versus many other places that are seeing cases rise right now, you do see vast differences in people’s responses to the pandemic and the precautions that people are taking and some of the policies that are put in place to restrict the transmission of disease. And so I think that’s a much, much more likely explanation for what’s happening. It really can’t be attributed to herd immunity, except for maybe in very small, particular isolated communities that have really seen a huge amount of transmission already. And there are very few of those.

Q: Excellent. Thank you.


MODERATOR: Next question.

Q: Hi, thanks for doing this. I have a question about the dynamics of where infections are happening and whether that’s changing, or where transmission is happening. And I know earlier in the pandemic, there was a lot of concern about workplaces and bars and restaurants. But now Dr. Birx is saying that these settings are less of a concern because people are following social distancing and mask wearing, and its social gatherings at people’s houses. That is becoming a big concern because people there are kind of being lax about wearing masks and social distancing. Do you agree with that? Have you noticed that pattern changing?

STEPHEN KISSLER: So I have not noticed the pattern changing in particular. It’s plausible, I would say. If it’s true and to the extent that it’s true that people are wearing masks and physically distancing in some of these other public indoor spaces versus private social gatherings. The difficulty in answering this question really comes down to the difficulty in contact tracing, which in turn comes down to again, the difficulty in testing. So to know where infections happen, we need to be able to trace those infections to a most likely source. And when there are large spreading events, we can do that pretty easily. So if there was a social gathering at someone’s house where many people became infected, then it’s likely that that’s where the disease spread. But in other circumstances, if there’s only a handful of infections, it’s hard to tell whether the infection happened at that gathering or at a grocery store or somewhere anytime within a couple of days surrounding that. When we’re doing contact tracing and we’re interviewing people about their activities over the past few days, you’re going to remember social gathering that you had, but you’re not necessarily going to remember every trip out of the house that you made.

So I think while that statement is plausible, I mean, I’m not saying it’s untrue. I think that may very well be true. And I certainly applaud the fact that people are wearing masks and maintaining physical distance in public spaces. And I think that ought to continue. And if that is truly contributing to reduced transmission in those public spaces, then all the better. And I imagine that it is. But that said, I think that if we’re looking at data on where infections are actually happening and whether it’s shifting, there are a lot of ways that that data can be confounded and really difficult to actually unpick what’s happening under the surface. And so I would take that with a grain of salt. Really, what I would say is just we should try to make sure that we’re being careful everywhere, both in public and in private. And as long as we’re doing that, then we should be OK.

Q: And the follow up question would just be what considerations should they make when they’re trying to decide whether they should lift restrictions on bars and indoor dining or reinstate restrictions when there’s questions about how big of a role those areas are playing in spread of COVID.

STEPHEN KISSLER:  Well, we run into the classic public health conundrum, which is that when Public Health is working, you can’t notice it because you’ve avoided a crisis that might have happened. But you can’t measure something that doesn’t happen. So I think that these are really difficult things to weigh in. As an epidemiologist, I can really only speak to the public health side. But of course, there are huge economic and social considerations as well with respect to opening up businesses and so I think that, as was true in the spring, reopening places that don’t seem to be major contributors to transmission can be done as long as it’s done slowly and carefully. And as long as there’s sufficient monitoring so that if those places do begin to contribute to transmission, we can stop or reverse course. So that will require first a fair number of patients. So opening them in stages and again, making sure that we’re doing testing and having testing available for example, for the employees of these places where transmission has historically been high risk like bars so that we can have a very clear sense of what’s going on. And so if cases do start to rise and those do start to become epicenters of transmission again, we can reverse course. But I think the most dangerous thing would be to say, well, it doesn’t look like they’re contributing much now, so we can just reopen and just sort of assume that they won’t contribute in the future. I think that would be a very good way of shooting ourselves in the foot.

Q: Well, thank you.


MODERATOR: Wait for a couple of moments. See if we have anybody. Any final questions? We do. OK, great.

Q: I’m working on a story about, you know, Brockton and how it’s approaching 5000 coronavirus cases. City of one hundred thousand people. And one of the dynamics I’m looking at, I’m just wondering if you could comment. Brockton, we’ve been told by our board of Health, has the largest number of frontline workers, people, essential workers who have continued working throughout the pandemic as compared to any other town or city throughout the state. And it’s also been one of the hardest hit cities by the coronavirus pandemic. I mean, what do you think about how having such a large population of people who had to continue to work? You know, people who work at grocery stores, hospitals, food manufacturers, we have a lot of them here in Brockton. How do you think that may have impacted the spread of coronavirus in our city? And how do you think businesses have dealt with this issue of people continuing to work throughout the pandemic?

STEPHEN KISSLER: So basically the story that you’ve just outlined, there is one that we’ve seen play out in many other communities as well. I keep going back to New York City because that’s where a lot of the information we have that’s available about major urban transmission of comfort comes from. And similarly, the communities that seems to get hit hardest in New York City were also the ones that had many people who were, it seems, continuing to go to work.

And so there are communities with many essential workers. And that, I think, in pretty clear ways, contributes to the spread of COVID because you’re just interacting with more people. You have more opportunities for spread. And that’s also confounded by the fact that many of the people who are working in these sorts of jobs that didn’t get as fully adjusted where grocery store workers and frontline health care workers. Many of them also, don’t have the means to protect themselves or to afford housing in places that aren’t shared. So I think that they face risks both in the workplace and at home. Frequently, they’re more likely to live in multi occupancy households. Things like that, which can also substantially contribute to the spread of COVID. So I think that there’s really this interplay of both of these things where they face risk at work and then they also face risk at home, which contributes to the spread of COVID on the whole. And so I think really what that underscores is that for businesses that are employing people deemed essential, that really a lot more needs to be done as we’re going into the fall and into the winter to protect these people, and I think concretely what that means is, of course, making sure that they have PPE available to them, masks and potentially face shields, depending on what sort of role they’re working in. And I think also making sure that there’s accommodations for taking time off, for taking sick leave, for not coming to work when one is sick. Really important. And being able to do that even without physicians, because we know that there are often barriers to health care for people who have lower financial means and may not even seek care at a doctor for it just because they can’t afford it.

And so making sure that those people have the ability to stay home if they are sick is really important as well. And then lastly, I feel like I say this every time I speak with anyone these days, but the testing is super important and to the extent that businesses can fund regular testing for their employees. That’s one of the single most important things they can do to reduce the spread of covered going into the fall and winter. So those things can’t happen on their own. I mean, they require funding. They require a lot of logistical organization, but they are things that need to happen because otherwise these communities will have already suffered. A lot will continue to suffer as we go into the fall and winter for sure.

MODERATOR: Are you all set?

Q: Yes. Thank you very much. Great answer.

STEPHEN KISSLER: Thank you. Appreciate it.

MODERATOR: Next question.

Q: Thanks again for the chance for a follow up. And maybe to touch on what you just talked about, you’d mentioned some of the needs that are still out there, including testing. I wonder if you can put contact tracing into that context. I know that you touched on this a little bit before. I had recently gotten some raw data from the CDC and I looked at our state and what they were turning in. And the vast, vast majority of cases, it appears, still are not contact traced in Illinois and I suspect around the country. And I’m wondering, you know, in your eyes, how important is that? And, number one, are you seeing that in the stuff that you’re seeing? And number two, how important is that? Is it just a luxury we don’t have? How hard is it? You know, just put it in context for me what we’re losing by not doing this.

STEPHEN KISSLER: So contact tracing is absolutely an important tool at our disposal here. One of the reasons I didn’t mention that is because we still have so much transmission in the community that in many places contact tracing just isn’t feasible. We just don’t have the people to follow up with all of the positive infections. So that’s part of it is just that since community prevalence is so high in many places, contact tracing becomes unfeasible. And so there’s a logistical limitation there. So absolutely. If we could do it, if we had the person power to do it, I think we should. But the limitations there are logistical ones. And those are, to my knowledge, harder to surmount than making more tests available. One of the other challenges with the contact tracing is that in many places, the turnaround time for tests is still pretty long. At best, it’s for PCR tests. It’s on the order of three to four days, some places still seven or longer. So by the time you actually get a confirmed case, you want to trace that person’s contacts. We have no idea when they were exposed. And by that, even if we were able to trace those contacts, those contacts have had contacts who have had contacts were already spread COVID. It just becomes this nightmare of being able to follow. So what we need to do to add contact tracing to that list in a reasonable manner is first, well, three things, actually, first, to bring prevalence down to a level where contact tracing becomes feasible or to increase the number of contact traces who we have available. And second, to really invest in rapid turnaround tests so that we can know a lot more quickly who’s infected and who’s infectious when they’re infectious so that we can trace their contacts in a much more limited span of time. So we know when they’re infectious. And so that we can catch those contact sooner so that they don’t go on to spread infection to others. But the unfortunate thing is that with the state of testing right now and with the state of prevalence right now, contact tracing just isn’t a very viable intervention in the United States at the moment. So I think that’s why we’re not seeing more of it.

Q: All right. Thanks so much. I appreciate it.


MODERATOR: It looks like that may be our last question. I have a quick one for you. Backward contact tracing has been used in other countries, but it has not been used so much here. Has it, that you’re aware of?

STEPHEN KISSLER: That’s right. That I’m aware of. And I think it’s a good strategy.

MODERATOR: Can you explain what backward contact tracing is, and why you think it hasn’t been used here as much?

STEPHEN KISSLER: So the idea behind concept backward contact tracing is that for many infections and especially infections like SARS-CoV-2, where most people don’t infect anyone but a few people infect lots of people. So there this propensity for super spreading events. So what that means is that if I get a positive test, I’m not actually that likely to spread to very many other people, but chances are that the person who gave it to me did spread it to many other people. So you can improve the efficiency of your contact tracing. By not tracing my contacts, but by tracing the contacts of the person who infected me. And that can be a lot more efficient way of of identifying who’s infected whom and who is at risk so that both from modeling and from experience in other countries, it seems that style of contact tracing can be especially effective for COVID. And I think that it is something that we should adopt here as we’re beginning to invest more in contact tracing. Again, I think that we have so many both metaphorical and literal fires burning here that it’s difficult to know where to start.

And so I think part of the reason it hasn’t been adopted is because there are so many other really basic things, including how do we implement mask wearing and how do we just bring prevalence down in the communities as a whole, that this is sort of one step down the line, which would be a very good to have. But I think there are other things that need to come into play first. But nevertheless, I think that we should be bearing this in mind as we’re beginning to ramp up contact tracing going into the fall, because it will absolutely help make that a more efficient and more effective process.

MODERATOR: OK. Thank you. I think that’s our last question. Any final thoughts you’d like to share with folks?

STEPHEN KISSLER: No, I don’t think so. It’s pretty comprehensive, so thanks, everyone, for being here.

This concludes the October 14th press conference.

View more press conferences