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Two local Covid-19 cases were found to be infected with the BA.4 variant, while one local case was infected with the BA.5 variant, the Ministry of Health (MOH) said in a press release on Sunday (May 15).

These are the first community cases confirmed to be infected with what the European Centre for Disease Prevention and Control has recently classified as "variants of concern".

The presence of BA.4 and BA.5 variants in these three cases was detected as part of the ministry's surveillance of the Covid-19 situation.

The cases were detected via further testing of polymerase chain reaction (PCR) positive samples and confirmed through whole genome sequencing (WGS).

All cases were either asymptomatic or had mild symptoms such as fever, cough, runny nose and sore throat; and did not require hospitalisation. They are fully vaccinated, and had earlier received their booster dose.

According to MOH, all three cases had self-isolated upon testing positive for Covid-19, and did not have any reported exposure to vulnerable settings.

Dominant variants in South Africa

The BA.4 and BA.5 variants were first reported by South Africa in early 2022 and have since become the dominant variants there.

Both lineages contain mutations in the spike protein which appear to "confer greater immune escape properties and higher transmissibility" compared to the BA.1 and BA.2 that caused the Omicron wave earlier this year, MOH said.

However, MOH added that emerging real-world evidence from other countries supports that BA.4 and BA.5 infections will likely give rise to "similar clinical outcomes", compared to previous Omicron lineages.

Citing figures from the World Health Organization, MOH said at least 1,000 cases of BA.4 and BA.5 have been reported in at least 16 countries as of May 11.

Calls on everyone to remain vigilant

MOH said it will step up local surveillance efforts and continue monitoring the spread of BA.4 and BA.5 in Singapore.

The ministry calls on everyone to continue to play their part and remain vigilant to mitigate the spread of Covid-19, even though society is now more resilient against the virus.

MOH said:

"In particular, persons vulnerable to complications of Covid-19, such as unvaccinated persons, persons above the age of 60, and persons with chronic diseases, should ensure they are up to date with their recommended boosters and exercise caution in settings with many potential contacts."

Top image by Roslan Rahman/AFP/Getty Images