askST: Are 12,700 Covid-19 cases in a week cause for concern?

SINGAPORE – Samples tested for Covid-19 over the past five weeks have returned a higher hit rate than those tested for influenza, though the number of severe Covid-19 cases requiring intensive care has remained low and is not likely to have a significant impact on healthcare capacity.

The estimated number of Covid-19 cases here rose to 12,700 in the week of May 10 to 16, compared with 8,000 in the previous week, said the Communicable Diseases Agency (CDA) on May 21.

CDA also said that the average number of daily Covid-19 hospitalisations rose from 56 to 73 during the same period, and it is monitoring the increase in infections.

Checks of CDA’s weekly bulletins reporting the number of communicable disease cases detected each week showed that the proportion of samples testing positive for Covid-19 has increased significantly since the week of April 5 to 11.

According to the bulletin for March 29 to April 4, 3 per cent of the samples of acute respiratory infections (ARI) collected tested positive for Covid-19.

This climbed to 7 per cent in the following week of April 5 to 11, and then 8 per cent over the next two weeks. It reached 14 per cent in the subsequent weeks of April 26 to May 2, and May 3 to 9, before easing slightly to 13 per cent in the week of May 10 to 16.

Under the National Surveillance Programme for ARI, patients with symptoms of these or influenza-like-illness (ILI) are randomly selected for testing to determine if they have been infected with Covid-19, influenza such as influenza A or influenza B, or other commonly circulating respiratory pathogens.

CDA bulletins also report the positivity rate of influenza each week, based on testing of ILI samples collected from polyclinics and general practitioner clinics. The rates have been lower than those of Covid-19 since the week of April 5 to 11.

In addition, Covid-19 infections have been among the top three ARI diseases detected in the surveillance testing for at least the last five weeks.

The Straits Times looks into the current Covid-19 situation.

Why is the number of Covid-19 cases an estimate?

Covid-19 has been part of the National Surveillance Programme for ARI since March 1, 2024.

Mandatory Covid-19 case notifications also ceased to be required under the Infectious Diseases Act since that day, according to CDA’s report on communicable diseases surveillance in Singapore from 2023 to 2024.

This means the number of Covid-19 cases is estimated from the positivity rate of the ARI samples collected, instead of actual numbers notified to the authorities.

Should we be worried with the high number of infections?

CDA said on May 21: “As with other endemic respiratory diseases, periodic Covid-19 waves are expected throughout the year.”

It also said there was no indication that the Covid-19 variants circulating here are more transmissible or cause more severe disease than previously circulating variants.

There was, on average, one Covid-19 case in the intensive care unit (ICU) each day based on CDA’s latest figures.

In comparison, the average ICU cases each day was around two to three when Singapore experienced an increase in Covid-19 infections in May 2025.

The NB.1.8.1 variant is the main variant circulating in Singapore currently and it accounted for more than half of locally sequenced cases, the agency said.

What is the NB.1.8.1 variant and is it more dangerous?

The NB.1.8.1 variant has been designated by the World Health Organization (WHO) as one of the variants under monitoring.

This means it contains genetic changes suspected to affect the virus’ characteristics, and has early signs of advantage, such as it might transmit more readily than other circulating variants, according to the WHO.

However, the WHO also said that evidence of the impact of these variants under monitoring is as yet unclear and will require enhanced monitoring and reassessment pending new evidence.

WHO data similarly showed that NB.1.8.1 is currently the most prevalent variant worldwide, accounting for 32 per cent of all sequenced cases for the week ending on April 26. The proportion increased from 22 per cent in the previous week.

The Covid-19 symptoms caused by the NB.1.8.1 variant are similar to those of variants that had led to previous waves, said Adjunct Associate Professor Monica Chan, a senior consultant at the National Centre for Infectious Diseases.

They include respiratory symptoms such as sore throat, cough, fever and muscle aches, as well as less common gastrointestinal symptoms such as nausea and diarrhoea, added Prof Chan.

In more severe cases, there may be shortness of breath due to pneumonia.

What led to an increase in infections?

CDA said on May 21 that several factors could have led to the increase, including waning population immunity. It did not elaborate on other factors.

The current vaccine is still effective against the NB.1.8.1 variant, said CDA.

Who should get vaccinated?

Those at increased risk of severe Covid-19 infection, such as those aged 60 years or older, including those staying in aged care facilities, and medically vulnerable people aged six months or older should have up-to-date vaccinations, said CDA.

Healthcare workers and those living or working with medically vulnerable people are also encouraged to take the vaccine, CDA added.