In a first, Hong Kong man gets Covid-19 twice

Man contracts a different strain after four months, is asymptomatic.

A man was infected with the coronavirus after recovering from an initial bout in April in what scientists said was the first case showing that reinfection may occur within a few months.
The 33-year-old's second SARS-CoV-2 infection was detected via airport screening on his return to Hong Kong from Europe this month. Researchers at the University of Hong Kong used genomic sequence analysis to prove that he had been infected by two different strains. The information technology worker didn't develop any symptoms from his second infection, which might indicate any "subsequent infections may be milder," the researchers said.
"Our findings suggest that SARS-CoV-2 may persist in humans," Kwok-Yung Yuen and colleagues said on Monday in a paper accepted for publication in the journal Clinical Infectious Diseases. The findings are reminiscent of the coronaviruses that cause the common cold, and suggest SARS-CoV-2 may continue to circulate "even if patients have acquired immunity via natural infection or via vaccination," they said.
While some patients have tested positive for the virus over many weeks, even after their symptoms have resolved, scientists haven't fully understood whether these cases reflect lingering traces of the virus, a re-eruption of an infection, or a new infection.
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 said in an emailed statement.