Wednesday, March 11, 2020

Epidemiologist Marc Lipsitch: The Coronavirus Isn't Going Away

I think that everyone should listen to epidemiologist Marc Lipsitch in order to fully understand the situation.


Transcript:   Many thanks to Ohad Benita who used Amazon AWS to transcribe the podcast and suggested Text Fixer to make it readable.

Noah Feldman:

From Pushkin Industries this is Deep Background, the show where we explore the stories behind the stories in the news. I am Noah Feldman.

Today we want to share with you a special episode, special because its subject matter just seems so pressing that we did not think it was appropriate to wait. We are going to talk to Marc Lipsitch about the coronavirus, covid-19. Marc isn’t just another expert on these topics. He is professor of epidemiology at the Harvard T.H. Chan School of Public Health and director of the Center for Communicable Disease Dynamics there. In other words, Marc is someone who has spent his entire career trying to understand the behavior of viruses and what they do when they spread around the world, and he is at the forefront of analyzing what’s going on with the coronavirus, right now, in real time. What Marc has to say … is more than a little bit disturbing.

Marc, thank you so much for taking time out of your busy schedule saving the world to talk to me. I am very, very grateful.

Marc Lipsitch:  Happy to do it.

NF: I want to start by diving into something you said to the Washington Post the other day, and I know that you said much more than this. They quoted you as saying there was a chance, and they didn’t say how big a chance, that 40 to 70 percent of the world’s population could end up infected with the coronavirus. And knowing you, you would never have said that unless you assigned some probability to that judgement. What did you actually say and what would you say about that subject?

ML: That is a roughly correct quote. I should have said of the adult population and I am trying to make amends for that, and I’ll explain that in a little bit, but I think that there is a very good chance that we are at the beginning of a pandemic of this novel coronavirus right now and that pandemic spread of that virus, given what we currently understand about its epidemiology, is likely to infect something of that order of the adult population. The reason for the adult qualification is that we don’t really understand what is going on with children, there are very few known cases in children. That either means that they are not getting infected, or perhaps means that they are getting  infected, maybe transmitting, but just sufficiently mild cases that we aren't detecting them with current surveillance.    

So, 40 percent infected does not mean 40 percent get very, very ill or that 40 percent die, but it does mean that some proportion of them gets symptomatic and of those, the current estimates are that around 1 or 2 percent,  may die,  with a very much larger risk of dying if you are over 65. So I really did say essentially what they quoted me as saying, and with the caveat about the adults, I still mean it.

 NF: Marc, what’s your confidence level in that 40 to 70 percent estimate?

ML: (Sighs). It’s hard to put a number exactly on that, sort of hyperprior, but I think the justification for it is that transmission of novel viruses with contagiousness level which we quantify as a reproductive number similar to this is something we’ve observed before and that is in influenza during pandemics, and in the two largest pandemics of the 20th century, around 30 to almost 40 percent of people became symptomatically infected, and that’s lower than the proportion that got infected, because some people don’t get very sick even with flu. So we have an analogue which is one reason for that number, and we also have mathematical models which are simplifications of reality, and we know that, and we don’t believe their outputs literally but mathematical models would say that it could be that range or higher  pending on how much  mixing there is in the population, so that's the basis for it. The ways it could be wrong are if transmission outside of China is fundamentally different in some way from transmission in Wuhan. If there's unexpectedly much benefit from warmer weather, we expect that the seasonal changes will modestly reduce transmission, but not very much, and certainly not enough to stop it. Or if interventions are sufficiently intensive, to as to stop the spread or very much slow the spread. That, I think, is a possible scenario, at least in certain places.

It's challenging because those interventions would have to be in place for a very long time, and we'll be very unpleasant for many people, um, more than  unpleasant, But I think probably another qualification that should have gone into that 40 to 70% is in the absence of strong countermeasures.

NF: Mark, when you say interventions. You're picturing quarantines, shelter in place, something stronger in terms of lock down. What? What's the kind of intervention that you're describing?

ML: There are kind of two categories, the one that I think increasingly we think won't work is isolation of cases and quarantine of their contacts and then making them isolate. I mean, I think that will be a part of it. And obviously people will self isolate to protect their family and to protect their contacts if they're sick and because they're sick, they will isolate to some extent.

But, it looks like those kinds of interventions by themselves probably aren't good enough for a virus like this, where there seems to be evidence of at least some transmission from people who are mildly ill or not yet ill. So I think the complement to that and the sort of more large scale interventions will be population level interventions where they don't depend on knowing who's sick and who's transmitting.

And those are things like canceling public gatherings, potentially closing schools, although the relevance of that is unclear until we understand better how children are involved in transmission and other kinds of  working from home and other kinds of ways of reducing contact between people, regardless of whether they're currently showing any symptoms.

And that's what the Chinese have successfully done, among other things, is very much clamp down on letting people out on the streets, because I understand that there's a sort of you can go out a certain frequency per week. You have to have a pass. You get your food and other supplies delivered with electronic payment. Not every place can do that, but some places can do that, to some extent, I think China, maybe one of the most, uh, able to do that of anywhere.  

NF: I want to talk about consequences now for a moment. In a world where, let's say, in the United States, between 40 and 70% of the adult population is infected on a daily basis. When it  reaches that depth of penetration, I assume you can't diagnose that 40 to 70% of the people you can only diagnose the symptomatic ones because there's just too many people and so do people more or less go about their daily lives or everyone is expected to more or less shelter in place except for the people who are necessary to preserve basic services?

ML: Ah, we're not going to identify every case, as you say, for the reasons you say it won't be 40 to 70% at the same time. Obviously it will take. It will go over some period of time. And the problem is, even if we could diagnose every one of those people, there seems to be some transmission, at least then maybe a fair amount of transmission from people who are not yet diagnosable.  So that's why I say there these two categories of interventions those that depend on cases and those that depend on general social distancing and for disinfection it's looking for now, unless our picture of it changes like the second category is gonna be more important. And unfortunately as we will see if China goes back to work as they're talking about doing those interventions only work while they're in place, as long as there's some virus still circulating when you let up on the interventions to keep people at home, transmission begins again.

So it is really a challenge, and the ways to get to the end of it, are either that enough people get infected so that transmission can't take off again, and given our current estimates, 40 or 50% would be enough to do that. The 70% scenario would be the sort of tail end of that after the virus is starting to go away.

But if 40 or 50% and this is very rough, because the numbers are changing about how contagious this is every time I have a phone call. But if say, 40 or 50% got infected, then that would be enough to prevent new outbreaks in that population until immunity declines, which it may do.

So that's one way, and all these control measures will make it more likely that that happens, at the minimum number needed rather than more than that minimum. And the other way is that we delay it long enough to have a vaccine. But I think the time scale for that is not realistic to do that for most of the world, in most of the world, unless we get extremely lucky with the quality and producibility of the vaccines,

NF  I think I'm experiencing some cognitive denial in listening to you, as I indeed I was when I read  your initial 40 to 70% estimate. So I guess I'm wondering if you could help me and help listeners in sort of taking on board whether we're just,  I'm just being irrational, you know?

Is my denial irrational? When I'm saying to myself I just can't picture a world where something like half of the U.S. population, adult population has coronavirus. Where was sort of looking at each other where you know every other person is infected at one point or another where, you know, potentially in United States, that would mean well over a 1,000,000 people could die and globally, obviously much, much, much, much more.

I mean, is my reaction just standard denialism or is there some underlying sense where maybe my skepticism is warranted in light of the imperfection of statistical projections?

ML: Ah, I think it depends on how, on whether you can find a reason to think that the pieces of the projections are wrong.

I mean, all projections could be wrong for reasons that we can't imagine so, So I'll give you 10% or even 20% chance that there's just something nobody's thought of that is gonna completely invalidate this, beyond that, you know, I've been thinking as hard as I can because I don't like the conclusion either.

I think the data on which we're basing this are not very good. So the bounds around what we're trying to estimate are very large. But, I mean, I think one way to think of it is this is not an existential threat, as the people who think about those things define it. This is a, really potentially a very bad thing that could happen that will touch many lives in a bad way.

But I think that's sort of how I'm thinking about it. And it's not fun to think about.

NF: You wrote a terrific piece in Scientific American trying to explain to the rest of us how we should think about what we read and hear. I think it will be great for listeners if you would share your three categories in your analysis, because I found it really helpful.

ML: Sure. Um, we wrote this because when I've been talking to journalists, I find that I'm constantly trying to hedge and say this is a fact, this is something I believe but isn't yet resolved as true or false.  And so the three categories that we laid out with Bill  and my colleagues were that when scientists talk about this pandemic, they can describe facts,  they can describe informed inference where facts are at the base of it, but some extrapolation is being made based on analogies to other viruses or information we know from different sources that we're putting together in a particular way.

And then the third category is opinion and speculation on topics like other people's motives, which are sort of irresolvable as matters of fact

But the first two categories I think, are interesting in that they're very fluid. So matters like whether there was undetected transmission in many countries that were matters of speculation informed by some calculations and facts, are now becoming matters of fact, meaning we now know there were a lot of undetected cases in Italy. There were a lot of in detective cases in Iran, but we could go - there were no detected cases in either place, and I wouldn't have picked those as the countries I would expect first to pop up. I would have picked perhaps Indonesia or some other countries, and I got a lot of flak for that.

But, the fact is, now we know there are cases in a bunch of countries where we were just speculating that because of the low amount of testing, we couldn't know and there probably was some. So I think in this epidemic, hopefully most topics are moving, uh, up the list from speculation informed by facts to real facts.

But the public health surveillance system is not set up, unfortunately, to provide factual answers to all these questions at once, because we just don't have ways of detecting things we've never seen before until we invent them and then those have to be rolled out, and so, for example, diagnostic testing is still a very, very limiting factor in many countries, including the U.S. So we don't know how many cases there are in this country because we're testing only people who have contacts with China or with known cases, and so if somebody was missed in this country coming through the border then anyone they infected in anyone those people infected and so on, is untestable under current protocols. That will change eventually, but at the moment we can't see them because we're not looking at them.

NF: And I take it that in your view, it's overwhelmingly probable that there are such people. I mean, you say you got flak for expecting more cases in Indonesia, but really, you should get some credit for saying that there were gonna be undetected cases, you know, somewhere, and sure enough, there were. So in that sense, there was a validation of your position.

ML: Yeah, um, thank you, I agree. I think that it's very, very likely that there are cases, many cases in this country that have not been detected and reading between the lines of statements from CDC officials, including the director, last week or two weeks ago, it seems as if they think that's probably true also in that they're saying they expect ongoing transmission. Robert Redfield, the director, said that he expected that this would be there come the next seasonal virus and which would be just with us for the long term.

NF: Your 40 to 70% in the adult population estimate, is that in category two for you, that's, you know, an inference based on, based on facts?

ML:  Yes, facts, models and analogies.

NF: And do you want to just say a word for listeners who might be interested about how you build those models. I'm fascinated by this. How do you go about doing this the rest of the time when you're not, you know, all the preparation as it were for when a potential pandemic actually does hit and suddenly you're, you know, on the front page of the newspapers making your predictions. But the rest of the time you're building the models and gathering the data. How do you, how do you go about that at the broadest level of generality?

ML: Yeah. Um, so I think the models that we work with are at their base very simple. They, they're models in which, in a computer on, ah, mathematical formula, you take one infectious individual on one susceptible individual. They bump into each other figuratively and create another infectious individual out of the susceptible. So it's like a chemical reaction, S + I = 2I. A susceptible plus infected equals two infected.

And then the other chemical reaction is infected yields recovered over some time scale.  That's in the   heart of all of these models. So, in the very simplest version of this, where we're all like, little atoms bouncing around in, ah, in an ideal gas.

If you build that model and put the parameters in that have been measured and estimated for this virus, you run it to its end and you end up with about 80 to 90% of the population infected, depending on which numbers you put in.

But we know that people are not ideal gases,    and there's structure in the population and their seasonal variability.  And there's different levels of susceptibility and then different age groups and things. And so when you're building a model for an infection that you know something about and where there's already data, you can incorporate all of those types of heterogeneity based on measurements from the data, sometimes with more certainty and sometimes with less and then you can run the model and see what happens.

And usually the almost always the ideal gas kind of approximation is the worst case, and all the structure tends to reduce infection levels, which is one reason I wouldn't have put 80% out there.

Uh, so that's kind of the approach. And then there are many kind of curly cues you can build on top of it that are ways of accommodating the particularities of certain infections. Like some infections there's a carrier state where you're not sick, but you are transmitting. Some infections you become immune and you stay immune. Others you become a little more immune and then a little more immune after multiple exposures. So you can elaborate that basic structure.

But the fundamental idea is that you're catalyzing new infections with old infections, and then people are recovering. Um, and everything else is a variation on that.
NF: Marc, what are you doing in your own real life? To prepare for this?

I mean, from what you're doing for your family to, did you cash out your retirement accounts out of the market and go into cash? I mean, I am just really curious in practical, real world terms. What? What are you doing?

ML: Yeah, I mean, I think at the moment we're all we're all a little in denial because this doesn't seem, it really doesn't feel real because nothing's happening visibly in our country.

So it's a process, and I think we're all kind of coming to the idea that if this scenario plays out as it feels like it might then we might be doing a lot of work from home. We might have our schools cancelled for goodness knows how many months.

And in the short term, you know, the recommendations from the government about getting supplies of essential goods, including medications, seemed like a good idea to me, not a year's supply, but a 90 days supplies is what they often recommend, and so we are trying to do that.

Obviously, the ability to do that is a luxury that not everybody has, and that's a problem.

NF: I mean, what are people anticipated to do about food if they're sheltering in place in that way?

ML: Well, I think that's a really good question. I'm kind of astonished how well it seems to have worked from what I hear in China, and my friends attribute that to the completely electronic economy that everybody uses phones to pay for things with one of the two systems that they have there so that eases things.

NF: So everything is basically being delivered. In other words, it's all being paid electronically and delivered

ML: Everything's being delivered, but of course there have to be delivery people, and those people have to have some contact with one another and with the warehouse and et cetera. And this has been thought through a bit in this country for just this reason when people were more concerned about bird flu pandemics. Ah, a decade ago. So I think we will have to see and it's not my expertise, but I am concerned about that as well.

NF: What am I not asking you that you think is important for people to hear?

ML: Um, in terms of preparing, I think the things that I described and just sort of mentally getting in the into the idea that there is a possibility, a significant possibility, of a really disrupted time is kind of my major recommendation and making some, some material plans for that in so far as people can.

NF: Where should people look up guidance on this if they they're not sure what are the essential medicines? I'm not sure I know what the essential medicines out of for 90 days, right?

ML: Well, what you have prescribed to you. There's not very many essential nonprescription medicines, but maybe some painkiller our anti fever medications, and there's a good website called , which has  lots of that information on it.

Politically, ah,  I think it would be good if people recognize that the administration has just asked for a tiny appropriation of two and a half billion dollars to deal with this, half of which is supposed to come from Ebola funding there was not yet spent. That's not a serious response. And ah, I hope that people will recognize that and press for more.

I hope they will demand better leadership than having the president say repeatedly again recently that this is all gonna go away the way stars did. SARS didn't go away. SARS was beaten back with very intensive measures, and this is much bigger than SARS.  So I think there's the political dimension to it.

I'm concerned also about the impact on our elections. If the virus really does start to be detected in more places in the United States, I think it could lead to people not wanting to go vote. In the primaries I think that could be used by various sides to try to make mischief over the results.

You know, I think there are lots of downstream consequences that we will understand better when we see them. But those are some of my concerns.

NF: Mark, I'm really grateful to you for speaking so clearly and so calmly about something that, as you say, doesn't really feel real yet and therefore is really susceptible to are powerful instinct to deny.

But, you know, as we all know, denying something doesn't mean it's not gonna happen. So I think we all do need toe change our mindset and start being a little more realistic about what the probabilities are as you've as you've laid them out.

So I just wanna really thank you for taking the time to clarify this and for saying a little bit about how you reached these conclusions. Getting behind the story can also help us, I think get to terms with the reality.

So really, thank you very, very much for what you're doing.

ML: Thank you for having me.

NF: Having spoken to Marc, I still am having trouble with my sense of unreality. I just don't want to believe what he's telling us about the 40 to 70% number of adults around the world who could end up infected with the Corona virus. And yet at the same time I know I'm talking to Marc Lipsitch.  I'm talking to a calm, reasonable, extremely brilliant epidemiologist who's made a career of studying the questions that he's working on now. If he is not the expert to be believed, there is no expert to be believed.

So I think what I'm gonna be trying to do going forward and maybe you'll choose to do the same, is to try to update my understanding of where we are and where we're going on the basis of his data.

When I do that, I admit it makes me afraid. But Marc also said very calmly that this is not an existential threat, or at least it's not an existential threat to society as a whole. So perhaps we can take a deep breath and perhaps take some small solace in that, even as we prepare ourselves for what could be a long and very difficult ride.

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