MARY LOUISE KELLY, HOST:
A few short weeks after states across the U.S. started to open up, several are starting to see noticeable spikes in their coronavirus cases. Nationwide, the virus is still killing more than 800 people every day. To talk about where this is headed, I am joined by NPR's global health correspondent Nurith Aizenman.
NURITH AIZENMAN, BYLINE: Hi, Mary Louise.
KELLY: So we know more than 100,000 people in the U.S. have died from COVID-19. You have been talking to the scientists who put together forecasts of the pandemic's course. What are they forecasting?
AIZENMAN: Well, the short answer, tens of thousands more deaths on top of what we've already seen between now and early fall. One model comes from Youyang Gu. He's actually not affiliated with any institution, just an MIT-trained individual. But his forecast has proved notably accurate, and it's widely admired by the experts. He projects more than 100,000 additional deaths by October 1. Today, another prominent team, the University of Washington's Institute of Health Metrics and Evaluation, they unveiled a forecast through October 1 of about 80,000 more deaths by then.
KELLY: And what is driving this?
AIZENMAN: Well, to get just a little technical here, what's key is what's called the reproduction number, or the R, which tells you for each individual who's infected, how many people do they go on to infect? When that number is above 1, that's what gives you an upward spiral, an exponential explosion in cases. So for example, if that reproduction number is 2, then that first person goes on to infect two others. Those two people go on to infect four people. Those four are going to infect eight, then 16. Within a month, that one person has launched a chain that has infected 127 people. So to stop that exponential growth, you need to bring this reproduction number below 1.
KELLY: Which was the whole point, as I recall, of all the measures that states took back in March - that we all, or most of us, were taking back in March. It was trying to bring down this reproduction number.
AIZENMAN: Exactly, those stay-at-home measures. And it makes sense. If people have fewer face-to-face interactions, then one person who's infected with COVID-19 is going to have fewer chances to spread it. And get this - say the reproduction number is brought way below 1, like 0.5. Then 100 people spread it to just 50, who spread it to 25. And eventually, the virus peters out.
Now during that stay-at-home period this spring, the U.S. managed to bring the reproduction number down - some states like New York by a lot. But nationally, we got it just barely below 1. And that means that, OK, we stopped this spiraling upwards, but we essentially only got things to, like, a steady state, each infected person passing it onto one new person, creating a kind of steady drip of new infections, which means every day, more deaths. And that over time adds up.
KELLY: And what you're telling us now is that as states and businesses reopen, that reproduction number is now rising.
AIZENMAN: Yes. So one of those modelers I mentioned, Youyang Gu, he's calculated that in about two-thirds of states now, the reproduction number has already crept up above 1.
KELLY: I have to ask, Nurith, whether we know, is it possible to know, is any of this due to the recent protests sparked by the death of George Floyd? I was out covering those protests. It is really hard to socially distance when you're in the streets with tens of thousands of people.
AIZENMAN: Absolutely. Now it's very hard to calculate the impact of that because we don't have a lot of previous experience to be able to say when people are in a demonstration, you know, how many get infected. On the one hand, yeah, you have people standing shoulder to shoulder, shouting. There also been arrests, which causes infections. On the other hand, it's outside. Many people were wearing masks. And, of course, it looks like a lot of the demonstrators skewed young, so those who do get infected are less likely to have serious outcomes. But there's an important point here that gets missed in that whole phrasing of the question, and that's one that was brought up to me by Marc Lipsitch. He's an epidemiologist at Harvard. Let's have a listen.
MARC LIPSITCH: Some transmissions will almost certainly happen at the protests. And the question is whether those lead to a lot of cases down the line or a relatively small number of cases down the line.
AIZENMAN: So what really matters is what happens after the marches. Do those who are infected at a march go into an environment where a high level of - where there's a high level of ongoing transmission, or a low level? Here's Lipsitch again.
LIPSITCH: How much transmission happens later on is far more dependent on our actions as a society and whether we can suppress transmission around the country than on how many people go to the protests.
AIZENMAN: In other words, you know, maybe the question we should be asking is not will the demonstrators cause a spike in COVID-19 infections, but will all of us - the public, officials - behave in a way moving forward that ensures that these marches and the improvements to racial equality that they might achieve down the line, that that doesn't end up coming at a cost of many more COVID deaths. In other words, it's really up to us.
KELLY: All right. And meanwhile, let me ask you a weather question, a seasonal question, because there was all this talk about a second wave that was going to come in late fall and the winter. What do we know about that?
AIZENMAN: Right, and this is a slightly confusing way to express it, this second wave idea, because, of course, we never really had a wave that crested. It just - we just started opening up before the daily cases could go down. But that said, yeah, Chris Murray, the lead researcher at the IHME modeling team, says that there's now enough evidence that the virus is seasonal to expect that when the weather gets colder, we are going to see another upsurge of cases. And that would be kind of in the, like, late September, October, really taking off in November.
KELLY: OK, a very sobering picture there from NPR global health correspondent Nurith Aizenman.
Thank you very much, Nurith.
AIZENMAN: You're welcome. Transcript provided by NPR, Copyright NPR.