A 33-year-old IT worker in Hong Kong came down with COVID-19 in March but recovered after experiencing mild symptoms. More than four months later, he returned from a trip to Europe and was diagnosed again, this time with a different strain of the virus. Researchers say his case is the first confirmed reinfection of COVID-19, reports the New York Times. While other reports of reinfections have surfaced anecdotally, this is the first to be verified by rigorous testing. Scientists at the University of Hong Kong sequenced the virus in both infections and discovered they didn't match, explains STAT News. Specifically, "there was a difference of 24 nucleotides—the 'letters' that make up the virus' RNA—between the two infections," the site explains.
The unidentified patient is experiencing no symptoms at all this time, which might suggest that the virus is milder the second time around. But it's important to "not jump to any conclusions" about what the case may or may not mean, says Maria Van Kerkhove of the World Health Organization, per Bloomberg. One reading of it might mean that the immunity people acquire from infection doesn't last as long as hoped, unlike the period of a few years for SARS and MERS. It's also possible that the man's case is an outlier and that reinfection is rare for COVID-19. Only time and more study will tell. But for now, "this is the world's first documentation of a patient who recovered from COVID-19, but got another episode of COVID-19 afterwards," the researchers say. (Read more coronavirus stories.)