Nevada health officials say the U.S. appears to have its first case of a COVID-19 reinfection.
A 25-year-old man there got sick in April, then recovered and tested negative twice.
In late May, he experienced symptoms again and tested positive.
Nevada's Public Health laboratory says genetic tests indicate he caught two different varieties of the virus.
"After one recovers from COVID-19, we still do not know how much immunity is built up, how long it may last, or how well antibodies play a role in protection against a reinfection," said the director of NPH.