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People who test positive again for the coronavirus, despite having already recovered COVID-19, aren’t being reinfected, a new study finds.

Reports of patients discharged from hospitals in South Korea testing positive after their apparent recovery had raised concerns that people could get infected by the virus in the short term more than once or that the infection could come back. But diagnostic tests for the coronavirus that causes COVID-19 rely on detecting the virus’s genetic material (SN: 4/17/20). A positive result does not indicate whether a person is shedding viruses capable of infecting cells — which would signal an active infection.

Now, a May 19 report from the Korean Centers for Disease Control and Prevention shows that samples from “reinfected” patients don’t have infectious viruses. The finding hints that the diagnostic tests are picking up on the genetic material from noninfectious or dead viruses. That lack of infectious virus particles means these people aren’t currently infected and can’t transmit the coronavirus to others, the researchers say.

“It’s good news,” says Angela Rasmussen, a virologist at Columbia University. “It appears people are not being reinfected, and this virus is not reactivating.”