A 33-year-old man who had recovered from a severe case of COVID-19 in April was infected again four months later in the first documented instance of human reinfection, University of Hong Kong researchers said on Monday. 

In August, after returning from a trip to Europe, he was diagnosed again—but with a different strain of the virus. While the first infection landed him in the hospital, the second produced no symptoms. Genetically, the first virus was closely related to strains collected in March/April while the second was closely related to strains collected in July/August, the researchers wrote in a report seen by Reuters. 

“Our findings suggest that SARS-CoV-2 may persist in the global human population as is the case for other common-cold associated human coronaviruses,” they said in a statement. “Since the immunity can be short lasting after natural infection, vaccination should also be considered for those with one episode of infection,” researchers said. 

“Patients with previous COVID-19 infection should also comply with epidemiological control measures such as universal masking and social distancing,” they added. The report has been accepted for publication in Clinical Infectious Diseases. — Reuters