AILSA CHANG, HOST:
Scientists have confirmed that a Nevada man was infected with the coronavirus twice. It is the first confirmed reinfection in the U.S, and it underscores the importance of social distancing and wearing masks, even for survivors of COVID-19. NPR's Rebecca Hersher is here with more. Hey, Becky.
REBECCA HERSHER, BYLINE: Hey.
CHANG: Hey. So what do we know about this case in Nevada?
HERSHER: We actually know a lot. The patient is 25 years old from a county in Nevada that includes Reno. He tested positive for the virus in April at a community testing site. And he had some symptoms at that point, including a cough. And then, we know that he recovered. The symptoms went away. And in May, he tested negative. Now, here's where it gets strange. In late May, he got sick again. He went to an urgent care facility, told them he had a fever, dizziness and a cough. And it appears that they didn't test him for the coronavirus at that point, maybe because he had already had it. In any case, he went home. He got sicker. The first week of June, he ended up in the hospital with low oxygen levels, and he tested positive for the virus again.
CHANG: Wow. And how can we be sure that he was infected two separate times?
HERSHER: Right. So scientists at the University of Nevada had the nasal swabs from his tests, and they sequenced the genomes on the virus bits on the swabs - basically, fingerprinted them to see whether they were exactly the same or different enough to be two different infections. And they found that they appear to be two different infections. So this is the first confirmed case of so-called reinfection by the coronavirus in the U.S. It's the fifth such case in the world. And there are a handful more that are suspected to be reinfections, but they haven't been confirmed with this kind of genetic testing.
CHANG: OK, so five confirmed reinfection cases like this worldwide. I guess my first thought is that doesn't sound like very many compared to the scale of this pandemic as a whole.
HERSHER: Right. You know, getting the coronavirus multiple times appears to be rare, although it's hard to know exactly how widespread this is because you need the genetic testing capabilities and the testing swabs from both the first and the second infection.
HERSHER: So probably there are people who have been infected twice, and it's flying under the radar.
CHANG: And do we know anything from this case, about why this might happen to some people versus others?
HERSHER: That is the million-dollar question. So, of course, immune system 101 is that a virus comes in, it triggers an immune response and the immune system creates antibodies - right? - that remember the virus and attack it if it shows up again in the future. So why didn't this happen in these patients? And the scientists I spoke to today, they said maybe the person was exposed to a much bigger dose of the virus the second time, or it's possible the immune response was more harmful than helpful the second time around. But honestly, those are just theories. Scientists say they need a lot more than five confirmed cases to really understand what's happening here.
CHANG: Right. Well, what does this mean ultimately for people's lives? Like, should we be adjusting our behavior as it becomes more clear that some people can be infected more than once?
HERSHER: That's a good question, right? And one thing that I think some people who have had COVID-19 and recovered from it might think is that they don't need to worry about the virus, but that's not really the case. And I asked Akiko Iwasaki, an immunobiologist at Yale University, about this.
AKIKO IWASAKI: What the reinfection cases emphasize is that even if you recovered first from infection, there's no guarantee that you won't be infected again, or you won't be transmitting the virus again during that reinfection.
HERSHER: So she says that means that everyone should be social distancing and wearing masks and washing their hands, even if you've already been infected with the virus in the past, even if you've survived COVID-19. And I think that's counterintuitive for a lot of people, but she says it's really important.
CHANG: That is NPR science reporter Rebecca Hersher. Thank you, Becky.
HERSHER: Thanks so much.
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