The Ministry of Health has performed further swab screening tests on preschool staff and uncovered 12 positive cases of Covid-19 as of Tuesday, May 26.

Previously, it was announced that seven cases were found — meaning that an additional five have since been detected.

33,100 tests conducted

The 12 positive cases were uncovered from a total of 33,100 tests that were performed on preschool staff as of May 26, MOH director of medical services Kenneth Mak said at a virtual press conference on Thursday, May 28.

This represents 0.036 per cent of the total tests conducted, he added.

11 tested positive in serological tests

In addition, he said that the 12 staffers were also sent for serology tests, in which 11 tested positive, while the test result for one remaining staff member is still pending.

According to the MOH in a May 12 press release, serology testing helps medical professionals understand the progression of the disease in the population, and thus manage the outbreak.

MOH also said that Singapore has used it in its research and among selected populations, and will use it among the migrant worker population as well.

Old infections that are no longer infectious

Mak explained that the serological and PCR (polymerase chain reaction) tests done on the preschool teachers were critically evaluated, and the evidence suggests that these are not active or fresh infections, but are old ones.

Therefore, the test results suggest that all the staff who were infected have recovered, he said.

MOH has assessed that none of the staff members are currently at risk to other colleagues or children in the preschool setting, Mak added.

He said: "This of course means that they are not infectious, and are less of a concern."

While MOH is unable to say exactly when the preschool staff were exposed to the virus, and therefore have gotten infected themselves, the majority of them are asymptomatic cases, he added.

All of them are well, and have made a "full recovery", he said.

Mak added that while there was some level  of community spread before the circuit breaker was imposed, the number of community cases have dropped significantly after circuit breaker measures were put in place, therefore proving that these measures have been "effective".

Top photo via Minister Desmond Lee's Facebook page