The Centre for Health Protection said the officer, who lives in Yau Tong and is based out of the force’s Wan Chai headquarters, started feeling unwell on Friday and was found to have a high viral load.
Chuang Shuk-kwan, head of the CHP’s communicable disease branch, said the officer tested negative while in hospital, but there’s no evidence that the case involves a contaminated specimen, which has happened before to other confirmed patients.
“After hospital admission, repeated samples may turn negative,” she said. “We understand that the specimen taking and testing, they may vary, in different times and locations. A small proportion of cases may not have antibodies.”
A microbiologist at the University of Hong Kong, Siddharth Sridhar, said this was unusal and further investigations should be carried out.
“We have had so-called ‘false positive’ cases in the past, but most of them have had a very low viral low which might be compatible with a laboratory contamination,” he said.
“It would take quite a gross mishap on the laboratory’s side for a negative sample to become a high viral load sample, so further investigations are required to see if he actually is a genuine case or a false positive case. I understand he had symptoms, so we do have to look for alternate causes for his symptoms as well,” Sridhar added.
He said Hong Kong should remain watchful before jumping to conclusions or panicking about this particular case.
The policeman normally works on a patrol squad, and had accompanied arrested persons on May 21 to the Chai Wan police station, and to the Lai Chi Kok detention centre on May 24.
Chuang said there is a mechanism in place to guard against the spread of Covid-19 among detainees.
“I understand all [new] detainees… will be separated from other detainees, at least for the initial days. They’ll be tested regularly,” she said.
“Of course, there’s still risk of spread, that’s why we have to put them into quarantine,” she added.”
Chuang said the officer has recently been to a number of restaurants as well as the food court in Lok Fu Place.
His two children have tested negative for the virus, and the schools they attend have suspended classes for a few days pending test results on others.