SINGAPORE — The authorities will be revising the criteria for the discharge of Covid-19 patients such that those who are clinically well by the 21st day after the onset of illness can be discharged without the need for further testing.

As an added precaution, however, these patients will have to remain at home or in dormitories for another seven days before they can return to work.

Health Minister Gan Kim Yong, who was speaking at a press conference by the governmental task force handling the crisis, said on Thursday (May 28): “This revised approach will allow recovered patients who are well and no longer infectious to return to the community in a timely manner.”

He added that it is also to ensure patients can receive optimal care and medical resources continue to be deployed effectively.

The Health Ministry's director of medical services Kenneth Mak said the new measures would free up testing capacity that can be redeployed to other settings requiring tests more urgently, such as in the migrant worker dormitories or in populations with vulnerable individuals.

The move to adjust the criteria was decided based on research here and overseas, which shows that Covid-19 patients are no longer infectious after Day 21 of the respiratory disease, Mr Gan said. 

This is even though they still test positive for the coronavirus during polymerase chain reaction (PCR) testing, which is the test now used to confirm patients with Covid-19.

Explaining the research behind the new criteria, Professor Leo Yee Sin, executive director of the National Centre for Infectious Diseases, said that three studies were done in Singapore to arrive at the new recommendations.

In the first one, which studied the first 18 local Covid-19 patients, researchers found that the virus shed the most during the early stages of the disease. The viral load in the infected patient then declined over time.

The second study analysed 766 patients and found that 30 per cent had cleared the PCR tests by the time they reached the 15th day of clinical illness. 

By the 21st day, 68 per cent of the patients were able to clear the PCR tests and most of the patients were able to clear the tests after the 33rd day of the illness — over a month after the onset of symptoms, Prof Leo said.

This suggests that only a small number of patients continue to test positive during the PCR tests for a very long period, she added.

In the third study, researchers took respiratory samples for culture from 73 patients. They found that when the viral quantity was too low for the researchers to sample the culture, patients would have been in the 10th or 11th day of the illness.

Prof Leo said this gives confidence that no viable virus can be cultured from respiratory samples of Covid-19 patients from Day 11 of clinical illness.

Mr Gan was asked by the media whether the authorities have made other plans to prevent further community transmission, in case NCID’s research is inaccurate. 

In response, he said that aside from local research, the Government also took into consideration scientific evidence from international studies as well as recommendations from the World Health Organization (WHO). 

WHO had recommended that symptomatic Covid-19 patients stay isolated for a minimum of 10 days. Within this period, the patients should be free of symptoms for at least three days before they can be safely discharged without the need for further testing.

For asymptomatic patients, the international health body said patients should be isolated for at least 10 days, as these patients do not show any symptoms.

Mr Gan said that Singapore is, in fact, being “extra safe”. Under the new criteria, patients will be discharged only after 21 days from the onset of illness — 10 days more than WHO’s recommendation.

He added that extra precaution has also been taken as the patients have to stay home for another week before they can return to the community.

Echoing Mr Gan’s remarks, Associate Professor Mak said patients will also be recommended to take a further leave of absence for another seven days to fully recover before returning to work.

Those who have suppressed immune systems will also be discharged based on the previous criterion of needing two consecutive negative swab test results.

“This is because these individuals who are immunosuppressed may not behave in the same way as others when it comes to dealing with infection and recovery,” said Assoc Prof Mak.

He added: “As we return Covid-19 infected patients back into the community, we want it to be a safe process such that there should not be any concern for further spread of infection from these individuals to other members of the community.

“This was the same approach and same principle that we had followed when we previously advocated the protocol of needing two consecutive negative swab tests before we discharge patients.”