Hong Kong researchers reported on Monday what appears to be the first confirmed case of coronavirus reinfection.

A 33-year-old man was first diagnosed with Covid-19 in late March. He only had some mild symptoms. He was hospitalized on March 29 and discharged on April 14, after the symptoms subsided.

Four months later, after the patient returned to Hong Kong from Spain, the second infection occurred. According to the researchers, the second infection was a slightly different virus strain from the previous one.

During his first encounter with the disease, the man had classic Covid-19 symptoms, including cough, fever, sore throat, and headache. Four months later, he did not develop any symptoms, the doctors said.

The finding suggests that some patients who recovered from the novel virus may only have a short-lived immunity. Besides, it is also significant for researchers who have been working on treatments using antibodies from recovered people. However, it is not enough to draw any conclusions.

Akiko Iwasaki, a professor of immunobiology at Yale University, was not surprised by the news. She said that it is no cause for alarm, and it is not unexpected, especially for the academic community. “It is not a cause for panic,” she noted.

Prof. Iwasaki highlighted that the man’s immune system might not be enough to prevent reinfection; it did appear to protect him from developing the disease caused by the virus. It means that the patient’s immune system managed to produce antibodies to fight the infection.

Prof. Brendan Wren, a microbiologist at the London School of Tropical Medicine, also said that the case is not unusual. It is a ”rare example,” he noted, adding that it is normal to find different virus strains as the virus will naturally mutate over time.

Dr. Anthony Fauci, the US leading virologist, already commented that the immunity to other, more well-known types of coronaviruses usually lasts between three to six months. For instance, its cousins SARS and MERS produced long-lasting resistance of several years. Fauci also emphasized that it could be completely different with the novel coronavirus.

Doctors have already reported numerous cases of presumed reinfection nationwide and elsewhere. None of those cases have been confirmed with proper testing.

Some 24 million people worldwide have been infected with Covid-19, the World Health Organization’s technical lead for the disease Maria van Kerkhove said. In her view, it is essential to document cases like the one in Hong Kong to understand the durability of the virus better.

What do you think? Shall we take additional measures such as a mandate for face masks nationwide?