SCOTT SIMON, HOST:
Corona infections are on the rise nationwide. Around 800 people are dying each day. And on Friday, the CDC warned that if cases begin to go up dramatically, the U.S. may need to return to stricter mitigation measures. NPR's global health correspondent Nurith Aizenman joins us. Nurith, thanks for being with us.
NURITH AIZENMAN, BYLINE: Hi, Scott.
SIMON: Where are the numbers going up? What are hotspots now?
AIZENMAN: So California, Florida, Texas now reporting their largest daily new infections to date. Also worrisome, Arizona. Three weeks ago, it was seeing less than 400 new cases a day. Now the daily average is more than 1,200. In a similar boat, Utah, South Carolina. But even in states where the numbers don't look so bad, there's a troubling trend. And to talk about it, I want to get just a bit technical.
SIMON: That's fine. We need to hear it, please.
AIZENMAN: OK. So a key indicator is what's called the reproduction number, or the R. It tells you, for every person who's infected, how many people will they go on to infect? Now, if it's above one, the virus spreads exponentially. For instance, it's estimated that before the U.S. stay-at-home orders, the reproduction number was above two. So think about it, Scott, let's. Say you're infected with the virus. Then you would go on to infect two others, who go on to infect four, who infect eight, 16 - that upward spiral happens fast. So the key is to push that reproduction number below one. And we did that during the stay-at-home period, but we only barely pushed the reproduction number below one. And that means that while the infections weren't spiraling up, we reached almost a steady state, this kind of drip, drip of new infections and new deaths each day. Ashish Jha is the director of the Harvard Global Health Institute. He says if this status quo continues...
ASHISH JHA: We're going to continue seeing 25 to 30,000 additional deaths a month. So this is really quite bad. And the level of virus and the level of disease burden in our country is very, very large.
AIZENMAN: And then on top of that with the reopenings, in two-thirds of states, the reproduction number has already crept up past one again.
SIMON: Is this the second wave that people were worrying about?
AIZENMAN: Right. The term second wave can be misleading because, of course, we never actually ended the first wave. We've just been chugging along. But that said, there is growing evidence that come autumn, we will move from this kind of steady state situation to a steep rise in cases.
SIMON: And that sounds alarming. Tell us what we need to know.
AIZENMAN: Well, so on Thursday, a prominent forecaster from the University of Washington, Chris Murray, said that when his team analyzed the curve of COVID-19 cases so far, they find that it's followed a seasonal pattern that's very similar to the seasonal pattern for pneumonia in the U.S. Namely in the warmer months, pneumonia cases go down.
SIMON: If it is seasonal, why doesn't it basically disappear in the summer?
AIZENMAN: Right. So when there's a totally new virus like this one, we have no immunity - it rips through us. So even if the warmer months slow down the virus's ability to spread, there's still going to be so many of us who are ripe for infection that the seasonal effect will be small. But come autumn, Murray says the seasonal effect really could make a difference with case counts. Let's take a listen.
CHRISTOPHER MURRAY: We start to see a powerful increase starting in early September. These numbers will intensify through February.
AIZENMAN: So he says seasonality will be a very big driver of the second wave.
SIMON: NPR's Nurith Aizenman, thank you so much.
AIZENMAN: You're welcome. Transcript provided by NPR, Copyright NPR.