• Having two Covid-19 cases detected in and around Tekka Centre suggests a possible link, either between the two or from an infected customer, one expert said
• It is expected that community surveillance testing will pick up people who are asymptomatic as well as those who have recovered from Covid-19, experts said
• It is practically impossible to identify all cases because individuals may show no symptoms
• The risk of local transmission remains as long as there are imported cases

SINGAPORE — Singapore will remain vulnerable to transmissions within the community as long as there are imported cases, health experts told TODAY after two people were found to have been infected by the coronavirus during a community testing of stallholders in and around Tekka Centre.

As for the two newly uncovered cases, they said that there is no cause for alarm because these were likely to be past infections and could have occurred anytime between two weeks and a month ago.

Dr Ling Li Min, an infectious diseases physician, said it is expected that community surveillance testing will pick up people who are infected and have no symptoms as well as those who have recovered from Covid-19.

A testing operation was conducted among 876 stallholders in and around Tekka Centre last Thursday (Nov 26). The Ministry of Health (MOH) then reported that two people were found to have Covid-19.

One is a 60-year-old Singaporean stallholder selling mutton at Tekka Market, the other a 41-year-old work permit holder from India who works as a warehouse assistant.

Dr Ling pointed out that there is not enough evidence to indicate that there is a new community cluster yet.

However, Associate Professor Alex Cook told TODAY that having two cases in and around Tekka Centre suggests a possible link, either between the two or from an infected customer. The recent cases also signify that there was a small amount of community transmission possibly a month or so ago.

Assoc Prof Cook, the vice-dean of research from the Saw Swee Hock School of Public Health at the National University of Singapore, said: “So far, there haven’t been any cases there who have been swabbed positive but are serologically negative, which would signal a recent infection.

“That means there’s no evidence of a current risk there, apart from the obvious factors that it’s a busy and popular place.”

SHEDDING VIRUS

Serology tests detect the presence of antibodies and can show if the person might have been infected in the past. This is different from polymerase chain reaction (PCR) tests, which are routinely used to determine if a person has any virus or is shedding it.

Nevertheless, Dr Paul Tambyah, an infectious diseases expert, referred to a study here that found that 10 per cent of individuals test serologically positive in the first six days of acute infection.

The president of the Asia Pacific Society of Clinical Microbiology and Infection said: “Thus it is possible that these individuals who were infected in the last week or two are still shedding either live virus or virus particles, hence their swab PCR tests were positive.”

NOT POSSIBLE TO IDENTIFY ALL CASES

Dr Leong Hoe Nam, an infectious diseases physician in private practice, said that it is practically impossible to identify all cases because individuals may show no symptoms.

The virus in certain individuals may also take a long time to shed even though they are asymptomatic or non-infectious, he added.

“Hence, it is not surprising that practically all countries have new cases popping up every now and then,” Dr Leong said.

Dr Tambyah said that the risk of local transmission remains as long as there are imported cases.

“Ultimately, this suggests that as long as the virus is circulating widely anywhere, an open and trade-dependent society like Singapore will remain vulnerable to local transmission," he said. “It is good that these cases were detected, hopefully before they start new clusters.”

He added that the extent of community spread could be identified through good “backwards and forward” contact tracing — where contacts who are the source of infections can be identified through serological testing and contacts who were infected can be identified through swab testing.

MOH earlier said the Government has been testing more extensively in the wider community to facilitate the early detection of the coronavirus and to obtain a better picture of the population prevalence to the disease.

So far, it has conducted such surveillance testing for those with higher risks of being infected given the nature of their working environment, such as taxi and private-hire car drivers, as well as food delivery personnel and stallholders at hawker centres.

NOT TOO CONCERNED

Stallholders at Tekka Centre who spoke to TODAY during a routine cleaning on Monday said that they are aware of the cases there but they are not too concerned.

Mr Amanullah Mohd Abdullah, a stall assistant of Royal Dum Briyani, said that he was initially a little worried because he occasionally bumped into one of the two men who were infected at the food centre.

However, the 73-year-old is confident that by wearing a mask and keeping a safe distance, these practices will safeguard his health.

Mr Adaikkalam Udai, a 50-year-old stall assistant of Buni’s Tiffin Corner, said that he was more concerned about how the news would hit the business.

“We take care of ourselves and look after each other here at Tekka Centre… So I’m not worried,” he added.