Coronavirus (COVID-19): Press Conference with Marc Lipsitch, 03/23/20


You’re listening to a press conference from the Harvard T.H. Chan School of Public Health featuring Marc Lipsitch, professor of epidemiology. This call was recorded at 11:00 am Eastern Time on Monday, March 23.

Previous press conferences are linked at the bottom of this transcript.

MARC LIPSITCH: Good morning, everyone. I don’t have a whole lot to start with today. We’ve talked many times in the past. I’ll point to the op-ed that I published this morning in The Washington Post suggesting how our testing strategy can best be adapted to the situation that we’re in in the United States, which is one of little testing capacity and lots of cases that we don’t know about.

And I wrote that, in part, because I’ve been asked by a lot of people, both professional public health people and reporters, about what should the testing strategy be? And the view that I wanted to clarify is that that’s not a meaningful question until you specify really two things. One is, what proportion of the cases do you know about? Which is low in the United States and high in some places, some islands like Singapore and Iceland. And secondly, what is your testing capacity, which is low in the United States and high in some of those other places.

If you have high testing capacity and know about a high proportion of all cases, then it makes sense to make testing of all cases and case-based interventions like isolation and quarantine the centerpiece of your strategy. If, on the other hand, you’re in our situation where you know about a small fraction of cases and have limited testing capacity, that can’t work. Because we can’t test everyone. And focusing very intensive interventions on a small fraction of cases doesn’t really constitute an effective control strategy.

So that’s why in our situation, we want to get to the point where we can implement a Singapore- or Iceland-like testing strategy. But at the moment, that would be a foolish thing to do, because we would run out of tests and not significantly reduce the spread of the epidemic. So, it’s a situation-specific recommendation and builds on a lot of work that’s been done in the past and recently by our group and others on the theoretical dimensions of this. But it’s all pretty much common sense and driven by whether you can realistically count on stopping most cases by identifying them or whether you have to stop them without identifying them.

So, I’m happy to take some questions about that or, obviously, about other topics. And I’ll stop there.

OPERATOR: We’ll take our first question.

Q: Hi, thank you very much. So, absent a testing strategy that is effective in this country, do we next go to a messaging strategy? It seems that some states are telling people to stay home, closing non-essential businesses. And in places like Florida, that is not a statewide strategy. What is the most effective messaging?

MARC LIPSITCH: Yeah, great question. I think there are a lot of messages, which make this complicated. But the summary of those messages is, if we want to keep [INAUDIBLE] we have to slow transmission as much as possible. And we have to especially try to slow the transmission to the most vulnerable who are more likely to end up in the health care system.

That means if you have respiratory symptoms, especially if you have a fever and feel like you have the flu isolate yourself and keep yourself as far from everyone as possible. But especially from those in the vulnerable groups. We know that much of the transmission came from very mildly symptomatic or pre-symptomatic people.

In my view, the need for intense social distancing is very strong right now. Because we have been watching countries around the world, starting with China, and then Iran, and then Italy, and now Spain and others finding their health care system at least stretched, if not really overwhelmed by cases. And it looks a similar trend is emerging in some US states.

Not every state is at that point yet. But the reason for acting now is that it takes around three weeks between the time we start slowing the cases down and the time the health care system benefits. So, we should be thinking not how bad it is now, but how bad it would be if we don’t act in three weeks.

The reason for that delay is that people who get infected today typically take, on the average, around three weeks before they get sick enough to need intensive care if they’re going to get that sick. Obviously, most people don’t get that sick. But the small fraction that do are enough people that, in many countries, we’ve seen intense strain on the health care system. And to stop that, we have to act now to protect three weeks from now.

It’s very hard to intuit if you don’t spend your career thinking about these things. It’s very unintuitive that if you don’t see a problem now you need to act to stop it in three weeks. But we’ve got to all get it through our heads that that’s how it is and begin to act before we see the intense problem. And I think my physician colleagues around the country are clearly seeing that and begging their non-physician and non-health care worker counterparts to, as the pictures say, stay home to protect us the way we come to work to protect you.

And I think as it becomes more intense in a few parts of the country, I hope that those remaining parts of the country that are fortunately earlier in the phase of the epidemic see that and take action. I find it unfortunate that it’s taken us this long, and also unfortunate from what I’ve heard now from a reporter that the president is beginning to recommend that we maybe need to lighten up on the social distancing That seems very, very counterproductive.

OPERATOR: We’ll take our next question.

Q: Hi, Marc. Thank you for taking the question. You said that the need is intense right now for strong social distancing. How long, if you’ve had a chance to consider this, do we need to do that? As you know, there are reports out saying that to suppress the virus we need to social distance for a minimum of five months. Other reports vary. What do you think about this?

MARC LIPSITCH: I think– and by the way, you’ve been asking– the preprint that we’ve been working on on this topic is up on Dash, the Harvard server. And I just sent it to you in an email.

Q: Oh, great. Thank you.

MARC LIPSITCH: So, it really depends on how long we do it– I mean, the question is how long we do it the first time, how intensely we do it, and what other places in the world are doing. So, I think we’ve seen in China that something on the order of less than two months, because they cracked down exactly two months ago today, January 23, with the closing of major Chinese cities. And they’ve begun to let up and continue to have, so far, no reported cases. So, if you can achieve Chinese-style social distancing, it may be that you can get to an undetectable level of cases in something like six weeks or eight weeks.

On the other hand, it remains to be seen whether undetectable means zero or whether undetectable means the early growth of a very small under-the-radar epidemic, as happened at the beginning in China, in Wuhan. And it also remains to be seen how they managed to keep imported cases out, even if they have truly gotten to zero.

So, I think we have now a data point that says, from a modest epidemic in Wuhan– modest meaning it just barely crashed the health care system. So, it’s not that modest. And from a much more modest epidemic in other cities in China where it never got close to crashing the health care system, you can do a lot of good in six to eight weeks of social distancing. The question is now, if you start social distancing when you see your health care system crashing, as has happened in Italy and I fear is going to be the case in many parts of the United States that don’t seem to be getting with the program yet, then that means that you have more cases in the population and that it will take longer to get down to close to zero.

So, I think all of these are dynamic variables that it’s hard to give a fixed number for. But the worst you let it get before you start, the longer it will take to get down to a reasonable level, especially because most of us don’t expect the United States will be able to be as intense in its social distancing as Chinese cities were. So, we’ll have to see how it evolves in China and in other places as they get their epidemics under control.

OPERATOR: We’ll take another–

MARC LIPSITCH: I’m not sure where the five months number comes from. I haven’t seen that one.

Q: That’s in the Imperial College study.

MARC LIPSITCH: Ah, that’s– OK.

OPERATOR: We’ll take our next question.

Q: I have questions on two topics. And I’ll ask them separately. For one, I’m interested in serology tests. Can you explain if there are best practices for when these types of studies should be started and how many people to enroll or how to go about doing it to get the best sense of what you’re looking for?

MARC LIPSITCH: I think a lot of groups are trying to figure that out right now. And so, I think the short answer is no, because we’ve never had quite this situation. And no one did that research in advance. But some general principles are that you want repeated cross sections of the population that will tell you across different age groups. Although age may not be that important in this epidemic. But we need to find that out. Across different age groups, what is the proportion positive– as a way of monitoring whether we’re anywhere close to a level of herd immunity that would retard the spread of the virus or slow the spread of the virus.

In that regard, we expect very strong regional variation. So, one number for a country like the United States is not meaningful – probably at least individual regions of the country, and maybe even states, and maybe even sub-state level variation is expected. Just because when chains of transmission take off, it’s a random process. And so, no, I think, while it’s true that West Virginia has done almost no testing, and therefore, one reason it has so few cases is that it’s done so little testing, another reason is probably it is actually behind New York in terms of its epidemic, because it took longer to get started there. So, I think serologic testing is going to need to be quite stratified and spread out across the country.

In terms of how many to do, that’s an evolving question where we kind of need to do some before we can answer that question. Because we don’t really know for all the cases that we’ve seen how many under the radar cases are there. And there’s a famous rule of three in statistics that if you do x tests and none of them are positive, then you can say with 95% confidence that the population has less than 3 over x as the prevalence. So, for example, if you do 100 tests and all of them are negative, then that means you’re pretty sure that less than 3% of the population, 3 out of 100, have actually been exposed.

So, if you want to just get a quick sense, you could start with 100 and see if you get zero or more that are positive. And if you’re sure that those positives are real, then you could scale down the testing a little bit in future surveys. Because you’ll know that you’re looking at some single percent, at least, if not more. Whereas if they’re all negative, then you have to do more tests before you can really get a precise estimate of how many there are.

So, you need some positives in your sample. But you don’t know how many positives there are going to be until you start doing it. The key thing is to share information across places about what people are finding in real time, so that we can refine the testing strategy.

Q: And then on another topic, you were talking about, I guess, maybe the first wave of cases potentially cresting or ending in places like China. And I guess whether it’s in China now or in the US eventually, what needs to be done after that first wave of cases to either prevent, or delay, or minimize a second wave, anticipating that that will happen?

MARC LIPSITCH: Yeah. You need very intensive testing protocols in place, looking at ill people to enhance your sensitivity, looking at asymptomatic people to make sure you’re not missing cases, although you can’t do infinitely many asymptomatic people very often. Because they’re just spread out, even if you’re China. So, you need very systematic testing in place and a surveillance system that can make some estimate of what the actual prevalence is, so that you can react in time it you’re starting to get a signal of growing numbers of cases.

And then, ideally, if the numbers are really low enough, you really can do a more Singapore-like or Iceland-like strategy of really following individual cases rather than just social distancing. And you may be able to get away with potentially with less social distancing the second time around, because you’re also controlling the individual cases. But the feasibility of that remains to be seen and requires a lot of organization that doesn’t yet exist. But I think the more forward-looking states are racing to create the infrastructure. Massachusetts is. New York is. Washington is. Probably some others are that I don’t know about.

But that investment will pay off, because it will mean a much greater ability to know what’s happening and to both minimize the negative impact of interventions by putting them out only when they’re needed and also to minimize the impact on the health care systems by putting them on before the impact is felt on the health care system.

Q: Thanks very much.

OPERATOR: We’ll take our next question.

Q: Hello, thanks for taking my question. So, I’m in Germany. And here in Berlin today the Robert Koch Institute said that they’re starting to see maybe some initial signs of exponential growth in new cases flattening out. And that they’ve– I think they said by the middle of the week they’ll know whether this is the case or not.

I’m kind of wondering how we should think about that. Once the exponential growth starts flattening, how much longer do people have to remain socially distant? Is it possible for it to flatten and then just shoot back up? What should we think about in terms of time frames? And is it realistic to think that a week or two of staying in our apartments is really enough for this to slow down?

MARC LIPSITCH: I mean, I think the kind of car analogy, if you’re on a hill, is roughly the right analogy. So, if you’re sitting on a downhill and you put on the brakes, you’ll slow yourself down. And eventually you might come to a stop in new cases. That means there are some cases around. But they’re going down, because they’re only recovering and not being new infections.

And if you let your foot off the brake which is letting up on the intervention, then gravity will start to accelerate the car again. And as long as there are any cases still around, you will start to speed up and get more cases.

So, it’s not– to push the analogy beyond where it should be, a vaccine would be an emergency brake. And then you can let up, and you have another backstop. But in the absence of a vaccine or some other very extreme seasonal changes in transmissibility, which would be temporary but we can hope will be present– in the absence of some external factor, if there’s any virus around it starts transmitting again when you let up on social distancing.

So, flattening of the curve is the first step. That’s great. It’s much better than not seeing that. But that’s very different from having a decline in the number of cases, which is, in itself, still different from having no detectable cases or few detectable cases. So, it’s definitely good news. I don’t remember exactly the temporal sequence of when Germany put in social distancing. But it’s weeks ago, not a month ago, I think, if I’m not mistaken.

And so yeah, I mean, we should be thrilled to find out any good news about the trend in the cases. But that doesn’t mean it’s time to let up. That means it’s showing that the effects we were hoping for are beginning to happen, and we need to continue, unfortunately.

Q: Okay. Thank you.

MARC LIPSITCH: But that’s important, very important data. Because so far, we’ve– to my knowledge, really, there have been not too many places where we’ve seen how social distancing works, especially in the West. So that’s important to see.

OPERATOR: We’ll take our next question.

MARC LIPSITCH: Welcome back to the new phone call.

Q: Hi, thank you. I want to take it a little bit parochially to Massachusetts. And I’m wondering if you think– the advisory went out today for all businesses to close down. Is it soon enough? Do you think that that is going to flatten the curve in Massachusetts? Or is it too late?

And relatedly, now that we’re seeing deaths being recorded pretty regularly over the last two days, what does that tell us? We knew people were going to die, but does that say something significant about the status of the epidemic in this state?

MARC LIPSITCH: Well, I think it puts an even more intense human face on what people were suspecting, and probably what’s happening already, but just not being detected. Yes, I think it shows that Massachusetts is like– that we’re all human beings and susceptible to this virus, which is something that I hope will become more and more obvious to more and more people. Because delays are not good.

I think there’s no answer to when is too late. I think there’s a real risk that our health care system is going to get badly strained. From physicians that I talked to, they’re feeling the strain already in terms of shortages of personal protective equipment. That’s an intense strain already in Massachusetts and I believe almost everywhere in the country. And I personally know health care workers who have been exposed and probably have it. I actually don’t know what the test result was.

This is real for them. They’re very concerned about the lack of ability to protect themselves. And so, I think tightening the social distancing is absolutely the right thing to do. And I hope that other places that haven’t done it already will follow suit.

Q: But is it soon enough? I guess, if we’re already seeing people dying, we’re already seeing the ICUs starting to fill up, and it takes three weeks for this kind of social distancing to make a difference, it sounds like it’s too late. Right? We’re still going to see a pretty bad surge.

MARC LIPSITCH: It makes a difference immediately. It doesn’t slow the problem for the ICUs for three weeks, but it certainly– so I think, yes, we will continue to see growth in the rate at which people have bad outcomes in Massachusetts, because I believe the epidemic is probably still growing right now. And it takes weeks before someone infected typically needs intensive care or dies. So, I think we will see an accelerating rate of that. And so, in that sense, yes, it’s too late.

But earlier is always better. And I don’t envy the decision makers who have to make the decision between protecting the health care system and protecting lives in that way and also the very real cost of the social distancing. I think it’s really important for those of us who are pushing for intensive social distancing to say that we understand that it’s a costly thing, not just for luxuries, but for lives and well-being of a lot of people. And so, I think it’s as important to try to mitigate the effects of the mitigation as it is to do it.

And that’s one reason I’m happy to live in Massachusetts, which is a more humane state than some others that I know about. But it’s going to be hard even with the best efforts of the Commonwealth. And I think we’ve been dealt a bad hand. But so did everyone.

Q: OK. But it’ll make a difference? It’s just not– we’re still going to see some hard times before then. But it could–

MARC LIPSITCH: Yes. There’s every indication in the surveillance of influenza-like illness in the Commonwealth. And I think we might be able to see it sooner than a few weeks. Because it should turn up in other types of data. But I think that remains to be seen. Because the whole system is under such stress that the numbers are meeting something different than they used to.

Q: Yeah. Thank you.

OPERATOR: We’ll take our next question.

Q: We’ve had this sort of historic dilemma where some people say that infectious disease always gets a lot more attention than chronic disease, even in terms of disease burden in normal circumstances, not during a pandemic. And now there are questions about how big a price we are paying to fight an infectious disease in terms of other choices that have to be make like cancer care and heart care. And at what point will we have this sort of– or what kind of advice or guidance would there be for balancing these medical needs? When does the treatment become worse than the disease?

MARC LIPSITCH: It’s a good question. The reason why we pay attention to pandemics and to the early phases of pandemics even when they’re not yet competing in terms of casualties with seasonal infectious diseases or with chronic diseases is because they can grow so fast. And there’s no good answer to that question.

Bad disease is bad disease. And dying from an illness is bad regardless of what kind of illness. And it’s clear that reducing medical care for both prevention and treatment of other types of diseases is a cost that we’re going to pay.

On the other hand, one thing about a contagious disease is it not only affects the people, the patients, but it also affects the health care of workers. And if we don’t control this disease, then oncology nurses, and dietitians, and cardiologists are going to be at risk of getting it. And they’re going to be out of the office because they’re under isolation. There have been stories of many, many medical residents being quarantined when they first got exposure.

So not dealing with this problem is really not an option. There is a lot of collateral harm from dealing with it, but there’s a lot of collateral harm, particularly to the care of infectious and non-infectious diseases, if we don’t control it. So, it’s not to dismiss the concern, but it’s just to say that we have a limited number of options. And preserving the health care system is a good idea for all sorts of reasons.

OPERATOR: We’ll take our next question.

Q: Thank you. Thanks for taking my question. So, I’d like to ask about masks. Normally, I’m very happy to parrot what the public people tell us to say. But in this case, they said very clearly, people in general should not wear simple masks.

But now the wisdom on that seems to be shifting. There’s a whole bunch of do-it-yourself masks being made. Hospitals are telling their entire staff to wear masks when they’re in public places. And so, I wonder if you can comment on that, and particularly on whether it does seem to be true that the widespread use of masks made a difference or is making a difference in Asian countries where that’s the norm, with the ultimate question being, well, should we all be putting on bandanas when we go out?

This weekend, for the first time in Boston I saw lots of non-Asian people on the street wearing them. And I’m just wondering what your wisdom is on that.

MARC LIPSITCH: Yeah, I mean, I think we’re– I think you’ve put your finger on an important question. I think there’s not really hard evidence that mask wearing is beneficial. But there’s a fair amount of soft evidence that it’s at least not harmful and probably somewhat beneficial.

The public health message came in part because of a concern about shortages and the sense that it’s more valuable to protect health care workers than to protect low risk members of the general population. And so, I think if we had a highly organized federal response, we would have a lot more masks. And the fact that we don’t is a complete failure of not just the public health system, but the executive power in the country, in my opinion.

We have to increase production of masks. And we do have to make sure that the health care system gets them first. Or we’re going to have no health care workers, because they’ll be sick. And they’ll be in quarantine from unprotected exposures. And frankly, some of them might decide that they aren’t willing to work under the inhumane conditions of being told to interact with sick people without equipment that’s available in every other country in the world, almost– certainly every other rich country in the world.

So, I think it’s a really hard question. And I think the solution that you suggest of people making them– I mean, it is clear that surgical masks don’t stop virus from getting into your mouth and nose. Because the holes in the fabric are too big and the holes on the sides are even bigger. So, I think improvising masks and bandanas and stuff may be an 80% solution. But I think at this point there’s not a lot of data. And it’s a hard question.

Q: Well, what’s the sense of whether– so there isn’t a lot of data. But in these Asian countries where it’s absolutely the norm to just wear a mask if you go out these days, is there any reason to think that is making a difference?

MARC LIPSITCH: I don’t know.

Q: OK. Thank you.

MARC LIPSITCH: One of my most respected colleagues is a guy named Ben Colwing, British biostatistician who works in Hong Kong and has for many years. He’s written some materials on this question, which I keep wanting to read. And then–


I haven’t had a chance. I would recommend looking at what he’s written. And I think he’s sort of thought about it as carefully as anybody I know.

Q: Great, thanks.

OPERATOR: We’ll take our next question.

Q: To the earlier question about serological testing, there’s been some chatter about using it to identify specifically medical personnel who may have already been infected, so that they can return to work. And I’m wondering what you think about deploying such a test in that manner, particularly since there may be some indication that people can get re-infected?

MARC LIPSITCH: Yeah. I’ve publicly stated that I support that if we can verify that serologic positivity really is protective, it certainly is going to be – I mean, just from general principles without data from this epidemic, it will almost certainly be much better to have been exposed before than not, so those people will be protected at least as if by a not-very-effective vaccine and maybe as if by a fully-effective vaccine. So, we need to check to make sure the protection is real before doing that on a large scale. But I think it will be an important part of the strategy, because we’ll need to keep health care workers in action.

In terms of the re-infection, the most famous stories about re-infection have been individuals who tested negative and then tested positive soon thereafter. And pretty much every specialist I know of, including me, thinks that the most likely explanation of those stories is that the person, for whatever reason, had a negative test in between two positive tests. But it was the same infection. It’s really hard to prove that without – well, you can’t prove that for sure without maybe sequencing the viruses or something.

But it’s a much more plausible explanation given that swabbing is an imperfect art. And there are going to be negative tests in people who are shedding virus. And there are going to be people who have parts of their body where they’re shedding more virus and less virus.

Q: So likely those were false negatives?

MARC LIPSITCH: Yeah. I mean, it’s routine when you’re analyzing that kind of swab data to assume that you have some rate of false negatives and try to estimate it from the data. You can’t estimate rates from anecdotes. But it’s not normal to imagine that there’s – it’s not sensible to imagine that every test is 100% sensitive. That doesn’t exist.

Q: Thank you.

OPERATOR: We’ll take our next question.

Q: Hi. I was wondering sort of a couple of things. But one question I have is, what happened to the CDC? Why is it so invisible in this crisis? And what does that mean? And do you think that if budgets at CDC and at state public health hadn’t been cut so badly, how much of a difference would that make in the current situation?

MARC LIPSITCH: Yeah. I don’t know. I have a 20 – almost 25 or maybe more – year history of collaborating with valued colleagues at CDC. It makes me very sad to see the lack of really being out front in the way that they were in 2009, when Anne Schuchat was every day providing really good information and very available to the press.

I have huge respect for their professional wisdom and their ability to lead in a crisis like this. And I don’t understand why they’re not being allowed to do that. I think I’ll leave it at that.

Q: Thank you.

OPERATOR: We’ll take our next question.

Q: Well, I appreciate the opportunity for a follow up. I just wanted to ask, first of all, do you think that Florida should be, from your perspective, doing the more aggressive actions like a statewide shutdown? Or is that something you don’t want to comment on?

And then I just had another point. Florida has started to report hospitalizations by community. And since it’s clear that in every major metro area there’s been a spike in hospitalizations related to COVID, since it takes two to four weeks before an infection reaches hospitalization, as you mentioned, can we draw any conclusions about the widespread transmission in these communities? Because we clearly do not have the testing data that’s– it’s not coming through very quickly. There’s huge delays here as well. I appreciate that. Thanks.

MARC LIPSITCH: Well, so I was going to punt your first question, because I haven’t had time to study the data from Florida. But your second question gave me some of that data. So if, indeed, communities around the state are seeing spikes in COVID hospitalizations then it is past time to intervene to slow transmission. And the opportunities to impose social distancing in a place where actually the weather is permissive of being outside more – it doesn’t even have to be quite as painful in Florida as it would be in some colder places.

Not that people should gather in giant groups at Disney World, but that if you can sit outside and talk to your neighbor across the fence, that is social distancing. And it’s also more pleasant than what you have to do if you’re in a cold place. I think Florida should be doing what all the states that are experiencing an upsurge are doing and what the states that aren’t yet seeing an upsurge should be doing as a cautionary measure.

Hospitalization doesn’t take three weeks, typically. It’s more like two weeks, at least based on the data that we’ve looked at. It’s the intensive care that tends to take an extra week or so. And those are averages, of course. There’s a variability. But yeah, an uptick in hospitalizations is an indication that there’s a lot of transmission that’s not being seen. Because it’s a small fraction of all cases that go to the hospital. And it’s hard to exactly predict that, especially as a function of demographics. Because it’s more severe in older people.

But if you’re seeing a signal in that kind of surveillance, that is a sign that there’s a growing problem, or that there’s a real problem. And everywhere we know about it’s growing unless you control it. So, expect it to be double in a week or so and then worse in another week, unless there’s some kind of slowdown.

Q: Thank you.

OPERATOR: We’ll take our next question.

Q: Hello. Thanks for doing this. So, my question is about, say in a couple of months we’ve sort of been good enough at doing social distancing to calm the epidemic. I guess from probably more of a qualitative standpoint, what would the testing and public health tracing capability have to look like for you to feel comfortable relaxing society-wide social distancing measures and sort of remaining confident that testing and isolating new cases and tracing contacts can sort of pick up the slack?

MARC LIPSITCH: We’re still working on that. And I don’t really have a very good answer for you. But I guess you would first want to see that the intensive care excess demand has gone close to zero. Because that’s the thing that we’re sort of – probably the first choke point. You would want to see that all the syndromic – like the hospitalizations and things were back to seasonal baseline, as they’ve been in previous years. And you would need enough testing of mildly ill or healthy people to have a sense that you know about most of the cases, meaning that when you test 100 healthy people that you don’t have any reason to suspect – or more, that you have zero positives. 100 is just made up. So, when you test a large number. It depends on the size of the population and those kinds of things.

So, we’re a long way from that in terms of testing capacity. And we’re also a long way from that in terms of the burden of illness right now.

Q: Yeah, thank you.

MARC LIPSITCH: I think we’ll end the call there. Thanks to everyone.

This concludes the Monday, March 23 press conference.

Press conference with Marc Lipsitch, professor of epidemiology and director of the Center for Communicable Disease Dynamics (March 20, 2020)

Press conference with Barry Bloom, professor of immunology and infectious diseases and former dean of the School (March 19, 2020)

Press conference with Marc Lipsitch, professor of epidemiology and director of the Center for Communicable Disease Dynamics (March 11, 2020)