World's first reported coronavirus reinfection documented in Hong Kong

Researchers in Hong Kong report that a 33-year-old man was infected a second time with the novel coronavirus – more than four months after his first fight with the illness. His is the first documented case of reinfection.

The man had no symptoms the second time, suggesting that despite positive reinfection, his immune system was able to develop a response to mitigate the virus, the researchers reported Monday. 

“The second infection was completely asymptomatic — his immune response prevented the disease from getting worse. It's kind of a textbook example of how immunity should work," Yale immunologist Akiko Iwasaki told the New York Times.

Though cases of suspected reinfection around the country and elsewhere have been reported, none until now have been confirmed by way of genome sequencing. The Hong Kong researchers were able to establish that the man's first infection was a different strain of the virus than his second.

Dr. Jeffrey Shaman, an epidemiologist at Columbia University, told the Times that he remains concerned that "we may be subject to repeat infection with this virus," and that this new case does nothing to dispel that fear.

In this case, "natural infection created immunity that prevented disease but not reinfection," said Dr. Iwasaki. Because asymptomatic carriers are still able to spread the illness, to achieve herd immunity a vaccine "is needed to induce immunity that prevents both reinfection and disease," she concluded.