Denseness of wet markets may help virus spread: Experts

Some experts also suggest that the more infectious Delta variant may be to blame for outbreaks

Wet markets can fit a large number of people in a compact space, and people have continued to flock to them even during the period of heightened alert.

It is not surprising, therefore, that Covid-19 cases have surfaced there, said experts.

The increased number of cases recently might also be from a variant of the virus that spreads more easily, they said.

The cluster at 115 Bukit Merah View Market and Food Centre has 56 cases, said the Ministry of Health (MOH) yesterday, making it the third-largest open cluster. Precautions have also been taken at other wet markets after positive cases were found.

Stallholders at the nearby Redhill Market and Food Centre had to undergo mandatory Covid-19 tests earlier this week. Testing was also conducted for people working at the Telok Blangah Drive Food Centre and Market, which has been closed for disinfection till today.

Associate Professor Alex Cook, vice-dean of research at the National University of Singapore's Saw Swee Hock School of Public Health, said some wet markets may be quite compact relative to the number of visitors. He said the recent market clusters have a mix of three types of cases: market workers, visitors, and household contacts of cases. Household contacts, while epidemiologically linked, were not infected at the market per se.

"So the risk of infection within a wet market is not quite as high as it may appear from the size of these clusters," he added.

Professor Paul Tambyah, president of the Asia-Pacific Society of Clinical Microbiology and Infection, said the spread in well-ventilated open-air wet markets suggests the virus is transmitted through droplets or surfaces.

As to whether markets should be avoided, he said: "The key has to be vaccination. That is how every single viral disease from smallpox to measles to polio has been controlled."

The authorities have established a possible link between the Bukit Merah and Telok Blangah markets. MOH said on Monday that a Singaporean man, 42, who works as a hawker at the Telok Blangah food centre is a family member of a 47-year-old cooking assistant at the Bukit Merah market.

Professor Teo Yik Ying, dean of the Saw Swee Hock School of Public Health, said it is highly likely that the cases at the Bukit Merah and Redhill markets are linked, given their proximity to each other.

He added that malls and supermarkets have been where outbreaks were detected recently.

"I do not see them as a new weak link, but rather as a consequence of Singapore having to deal with a much more infectious Delta variant that is driving these outbreaks."

MOH told The Straits Times earlier this month that as at the end of last month, 550 Covid-19 cases here were of the Delta variant.

Prof Tambyah disagreed that the spread in wet markets was related to the Delta variant, noting that the very first super-spreading event was at the Huanan seafood market in Wuhan.