Since the lifting of the circuit breaker on June 2, the number of community cases has increased, although they continue to remain low with about an average of 12 per day in the past week, Health Minister Gan Kim Yong said during a virtual press conference yesterday.

But it is still not the time to celebrate and be complacent as the country is definitely not out of the woods yet, he said.

Around half of the community cases over the last two weeks were linked, and most were detected as a result of contact tracing or proactive screening.

The majority of the unlinked cases, or seven in 10 of them, were asymptomatic at the time they were tested, and almost half were likely to be past infections as they tested positive during serology tests, Mr Gan said.

Those who are asymptomatic remain completely so throughout the entire course of illness, while pre-symptomatic individuals are asymptomatic at the time of testing, and manifest some symptoms only a day or two later.

Asymptomatic cases are generally picked up during proactive screening, such as when the Covid-19 task force conducts regular screening of front-line workers. Some might be picked up incidentally, such as when the patient is suspicious and decides to get tested.

A large proportion of the unlinked community cases was classified as such because the task force was unable to identify the specific individual or cluster that passed the infection to them, but the cases appeared to be linked broadly to the construction and related sectors, said Mr Gan.

"We are keeping an especially close watch on the symptomatic unlinked cases that are detected in the community through our routine screening," he said.

The task force has also significantly scaled up testing of those with acute respiratory infection (ARI) symptoms at first presentation to the doctor, and is now testing around 2,400 ARI cases a day on average.