MARY LOUISE KELLY, HOST:
Many scientists believe the COVID-19 pandemic has entered a new phase over these last few weeks. More transmissible forms of the virus have likely cropped up on three continents. At least one variant is circulating here in the U.S. at low levels, but the Centers for Disease Control and Prevention predicts it could cause a big surge in cases here in March. And another variant 3,000 miles away has scientists alarmed for a different reason. NPR's Michaeleen Doucleff explains why.
MICHAELEEN DOUCLEFF, BYLINE: Back in April, COVID-19 hit the city of Manaus, Brazil, extremely hard. It's a city of about 2 million people in the Amazon rainforest. People were dying so quickly that cemetery workers dug mass graves with backhoes. Patricia Sicchar is a doctor there.
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PATRICIA SICCHAR: (Non-English language spoken).
DOUCLEFF: She told NPR at the time the population of Amazonas was being decimated.
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SICCHAR: (Non-English language spoken).
DOUCLEFF: "Ambulances carrying patients must wait outside hospitals because there are no beds." The outbreak in Manaus was arguably the worst anywhere in the world. One study published in the journal Science estimated that so many people were infected that the city could have reached herd immunity, that the outbreak there slowed down because so many people had protection against the virus. Now the city of Manaus is seeing another massive surge in cases.
Marcus Venecia Lacerda (ph) is an infectious disease doctor there. He says the second surge appears worse than the first.
MARCUS VENECIA LACERDA: I'm really afraid. I'm really afraid. I'm seeing lots of people dying, so the situation here now is of panic.
DOUCLEFF: Because hospitals are turning away people - they've run out of oxygen. Patients on ventilators are suffocating. In many ways, this resurgence doesn't seem to make sense because in Manaus, a large proportion of the population should be immune to the coronavirus. So why is the city seeing such a huge surge? Lacerda says part of the reason could be reinfections.
VENECIA LACERDA: So apparently, what is happening is that people who had some small exposure to the virus in the past are becoming infected now.
DOUCLEFF: Since the spring, people's immunity could have waned. On top of that, Manaus, like the U.K., has a new version of the virus that's spreading very quickly. This new variant, called P1, has about 20 mutations, including one that's especially concerning. In laboratory settings, this mutation helps the virus avoid or evade antibodies.
Ravi Gupta is a microbiologist at the University of Cambridge. He says mutations like this could make it easier for some people to get COVID-19 a second time.
RAVI GUPTA: Yes, I do, partly because we know that you can get reinfected even with the same virus, OK? So I think what this mutation will allow the virus to do is to more easily infect those who have already been infected, so your barrier for resistance to the virus has just dropped.
DOUCLEFF: But, Gupta says, no one knows yet how common these types of reinfections will be. The effect could be small. Jeremy Luban is a biochemist at the University of Massachusetts Medical School. He agrees that what's happening in Manaus is a mystery.
JEREMY LUBAN: The bottom line is I don't think we know yet. I think that these scenarios that people are worried about are plausible, and they're cause for concern. What we do know is that there is an absolute total disaster occurring there.
DOUCLEFF: Scientists have launched studies to determine what extent reinfections are happening in Manaus and if it's only time before they cause resurgences around the world.
Michaeleen Doucleff, NPR News.
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