Researchers find first US case of COVID-19 reinfection

Researchers have documented what appears to be the first U.S. instance of someone getting reinfected with COVID-19.

In a preprint of a paper submitted to the journal The Lancet, researchers said a 25-year-old man in Nevada was reinfected with the SARS-CoV-2 virus in late May, after recovering from a relatively mild case the month before.

Infectious disease experts said reinfections are normal and should be expected, and caution against drawing broad conclusions.

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Reports of reinfections this week have come from Hong Kong, the Netherlands, Belgium and now the U.S.

The patient in Nevada initially tested positive for coronavirus in April, after exhibiting symptoms including a sore throat, cough, headache, nausea and diarrhea. 

The patient eventually reported having no more symptoms, and subsequently tested negative twice.

But 48 days later, he started exhibiting symptoms again, with a much more severe case. He was hospitalized and required oxygen.

The researchers sequenced the RNA from both virus samples, and found they were two different strains, making it a true reinfection.

It's unclear why the patient was reinfected, and there's still not a lot of evidence about immune response in people who have been infected with the virus. 

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Generally, researchers are finding that people who get COVID-19 develop a healthy immune response, but it's unknown how long it lasts. 

The Nevada researchers wrote in the paper that one case doesn't prove a widespread phenomenon. The implication of reinfections is that a vaccine might not be able to give 100 percent protection, but they noted that is "an established understanding, with influenza regularly demonstrating the challenges of effective vaccine design."

Michael Mina, an epidemiologist at the Harvard T.H. Chan School of Public Health, said there are millions of coronavirus cases and the important question is what happens with large numbers of people.

In a tweet, Mina elaborated to say that to scientists, "the rare events are important because we learn from them — so we publish them. But unfortunately, academic reports get placed on front page of major media — confusing and scaring many."