The University of Hong Kong published a report confirming the world’s first coronavirus reinfection case. A 33-year old man from Hong Kong tested positive for the infection 142 days after he had tested positive for the first time in March. The patient was returning to Hong Kong from Spain via United Kingdom and was screened at the airport. Researchers from the University conducted a genome sequencing study to confirm the second instance of infection and to differentiate infection from viral shedding.
The medical community didn’t know how long people who got sick and recovered might be protected from infection. Every survived infection could bring a community closer to herd immunity. This is where so many people have become infected and then immune that the virus can no longer find enough vulnerable people to keep an outbreak going.Some isolated reports had emerged of people who had recovered from COVID-19 only to once again get sick with the virus. But without genetic data showing that each round of illness had been caused by two different viruses, it was unclear whether such cases were true reinfections. For instance, some common colds are caused by coronaviruses. And people can get infected over and over with these viruses. As our immune response to them wanes, we once again become susceptible to them.
The man had a fever, cough, sore throat and headache for three days in March. Late that month he tested positive COVID-19. The man was admitted to a hospital in Hong Kong 3 days later. By then his symptoms were gone. He was released on April 14. That was after he tested negative in each of two separate tests for the virus.But on August 15, this man again tested positive. He found out this when airport officials screened him upon returning to the Hong Kong from Spain. This time, the man showed no sign of being sick. It meant his immune system had kicked in to protect him.
Overall, it’s unknown how long immunity to SAR-CoV-2 lasts. Some people can test positive for the virus’s genetic material for months after they get well, and shed no infectious virus. A few studies measuring antibodies , key proteins that recognize and bind to germs suggest that their levels do wane with time. Some coronavirus work hints that antibodies to stop the virus from entering cells may remain in the blood for at least three months.The latest data, from just one person, might not reflect what usually happens, experts warn. Researchers will need to review more cases to know for sure.