Workers returning to Tianjin no longer infectious despite positive Covid-19 swab tests: MOH

SINGAPORE - Twelve of 14 passengers on board an Aug 19 Scoot flight from Singapore to Tianjin, China, who had a positive Covid-19 polymerase chain reaction (PCR) test result were not deemed infectious, while investigations are ongoing into the other two cases.

Responding to media queries on Tuesday (Aug 25), the Ministry of Health (MOH) said the 12 were recovered migrant workers who had lived in dormitories.

Individuals may continue to shed viral fragments for weeks or even months after infection which may lead to positive PCR test results, the MOH said.

However, the ministry said there is no evidence to suggest that these remnant viral fragments are infectious.

"Studies so far have failed to culture viable virus from these patient samples, indicating that these individuals are no longer infectious and are thus safe for travel," the MOH said.

At a virtual press conference last Friday, a reporter for China Central Television cited an incident in which returning workers who were cleared of the virus later tested positive for Covid-19, and asked the multi-ministry task force if there were differences in the tests used by the two countries.

In his response, the Health Ministry's director of medical services, Associate Professor Kenneth Mak, said: "On occasion, some of these workers may still have a positive PCR test, but all other tests done for them show that they are no longer infectious.

"We have no problems in certifying them fit for travel."

In its statement, the MOH cited World Health Organisation (WHO) guidelines, which state that the criteria for discharging symptomatic patients from isolation without requiring retesting is 10 days after symptom onset and at least three additional days without symptoms.

For discharging asymptomatic patients, only 10 days of isolation are needed following the first positive test.

According to Singapore's discharge criteria, which are more stringent than WHO's recommended guidelines, Covid-19 patients who are assessed to be clinically well at day 21 of illness are discharged.

The MOH said that this is based on the latest local and international clinical and scientific evidence which shows that viable virus was not found in Covid-19 patients after the second week of illness.

"Countries adopt different discharge criteria that may take into consideration factors beyond public health or scientific literature. Our discharge criteria have also been shared with the Chinese authorities," the MOH said.

The Health Ministry added that Singapore in contact with the Chinese authorities for further information on the remaining two cases.