SINGAPORE - Out of 1,120 fishmongers and assistants who were tested over the weekend, 30 were found to be Covid-19 positive, said Health Minister Ong Ye Kung on Tuesday (July 20).

At a virtual press conference by the multi-ministry task force tackling Covid-19, Mr Ong said that 28 markets and food centres have been linked to the Jurong Fishery Port cluster so far.

Of 182 new community Covid-19 cases announced on Tuesday, 142 are linked to the Jurong Fishery Port. This brings the total number of cases in the cluster to 321.

To stem the recent spike in community cases, the task force announced on Tuesday that Singapore would revert to phase two (heightened alert) restrictions from July 22 to Aug 18, with tightened measures such as no dining in allowed at eateries. Social gatherings will be limited to two people as well.

Mr Ong said when the Jurong Fishery Port cluster broke out, cases were almost immediately discovered at Hong Lim and Chong Boon markets. He added that it probably preceded the KTV cluster.

"We issued health risk warnings to the fishmongers which required them by law to get themselves tested and then isolated until they receive their test results," added the minister, saying the National Environment Agency was mobilised on Sunday to tell fishmongers to stop selling fish.

Said Mr Ong: "It was a nervous weekend, because we knew that hundreds and thousands of fishmongers and their assistants who visited the Jurong Fishery Port may have been infected, and then went out to the community to sell their fish... And because fish was in short supply, many shoppers, patrons and residents actually went to queue up for fish."

He noted that unlike the KTV cluster, the authorities are not seeing the numbers in the Jurong Fishery Port cluster decaying. They are instead still rising.

Singapore's director of medical services Kenneth Mak said the growing number of cases being picked up from wet market testing remains a cause for concern.

"A number of these individuals are seniors. It is not surprising, given the setting in which we found them (the cases) in the wet markets, as well as at the fishery port.

"We do know that those who are seniors have a higher risk of getting a serious infection and complications from Covid-19 infection... even dying from infection," he said.

Mr Ong said with at least one infected resident per market, testing has been widened to more people in the community, such as residents living in the blocks around the markets.

They have been advised to minimise social interaction and stay home, especially if they have unvaccinated seniors at home. This is to prevent spillover to the larger community.

Unlike the KTV cluster, which broke out last week and "spread among a younger population and certain network of people", Mr Ong said, the wave of infections from the fishery port affects markets, food centres and a much wider spectrum of the population, especially seniors.

"The porous nature of our food centres and hawker centres also increases the risk of cryptic and silent transmission that is hard to detect. Hence, after thinking long and hard, we decided we have to revert to phase two (heightened alert)," he said.

Seven cases linked to the cluster were reported on July 17, 42 on July 18 and 106 on July 19.

Of the 182 new local cases on Tuesday, Mr Ong said, 85 individuals, or almost 47 per cent, were isolated before detection.

"So, tomorrow, when you see the numbers go up, it means these cases were already quarantined and isolated... they are not passing (the virus) to others when they develop symptoms, so they are much less of a risk."

He added: "As you see that happening, you should also see us turning the corner, with the numbers coming down. That's how the trajectory often behaves."

Recent clusters: 119 cases detected so far from testing

Large-scale testing for people in places linked to recent and emerging clusters has uncovered at least 119 cases of Covid-19 infection so far, said Singapore's director of medical services Kenneth Mak. These are the numbers of people tested:

•More than 7,600 linked to Jurong Fishery Port and related wet market operations

•Over 3,400 linked to KTV clubs

•More than 3,100 linked to Hong Lim Market and Food Centre

•More than 1,800 linked to ComfortDelGro Driving Centre in Ubi

Health Minister Ong Ye Kung, co-chair of the multi-ministry task force tackling Covid-19, said the KTV cluster, which had 207 cases as at yesterday, is stabilising. "I think we will continue to see a downward trajectory," he said.

But the growing cluster linked to the fishery port that stood at 321 cases as at yesterday, is a concern.

Mr Ong said it has spread to 28 markets and food centres, "every one of which has at least one case, and the numbers are still rising". The number was raised to 35 last night.

"So this is the period, when we look at the cluster emerging, that every day makes a difference... The picture is now not entirely worsening every day... It's more mixed now."

Read next: What you need to know about Singapore's Covid-19 rules from July 22