550 cases of Delta variant in S'pore at end-May

Passengers queueing for taxis at Changi Airport's Terminal 1 on April 30. The Delta variant surfaced in the two biggest community clusters here in recent months - in Changi Airport and Tan Tock Seng Hospital.
Passengers queueing for taxis at Changi Airport's Terminal 1 on April 30. The Delta variant surfaced in the two biggest community clusters here in recent months - in Changi Airport and Tan Tock Seng Hospital.ST PHOTO: KUA CHEE SIONG

As at the end of May, 550 Covid-19 cases in Singapore were infected with the Delta variant of the coronavirus first detected in India.

This figure comprises 428 local and 122 imported cases, the Ministry of Health (MOH) told The Straits Times.

It did not say when the first case was detected but an infection on April 28 was later attributed to the Delta variant or B16172.

It is considered more easily transmissible from human to human, and was what fuelled the massive spread of the virus in India.

This variant was first picked up in India last October, but is believed to have made its way to Singapore only recently.

On May 4, MOH said in a press statement that there were seven local cases infected with the Delta variant in Singapore.

Last month, Singapore saw a total of 906 Covid-19 cases, of which 524 were local community infections.

The Delta variant is also believed to have sparked the Tan Tock Seng Hospital (TTSH) cluster, which was reported as closed on Sunday after no new transmissions were linked to it for 28 days.

Three deaths were linked to the cluster, including an 86-year-old Singaporean woman who died on Monday from complications due to Covid-19.

An MOH spokesman told ST that variants are detected through viral genomic sequencing.

This is done at the National Public Health Laboratory at the National Centre for Infectious Diseases for all confirmed Covid-19 cases, she said, unlike other countries which typically sequence a smaller proportion of their confirmed cases.

MOH figures also show that the number of local Delta variant cases in Singapore is the highest caused by a variant of concern, among four such variants that have been detected here.

Variants of concern are more easily transmitted from person to person.

As at May 31, a total of 449 local cases of infection involve a variant of concern. They comprise:

• 428 people infected with the Delta variant;

• Seven people infected with the Alpha variant, first detected in Britain;

• Nine people infected with the Beta variant, first detected in South Africa; and

• Five people infected with the Gamma variant, first detected in Brazil.

The MOH spokesman said: "We have adapted our measures accordingly and the number of locally transmitted cases has decreased over the last two weeks.

  • Local cases involving variants of concern

  • As at May 31, there were 449 local Covid-19 cases infected with variants of concern, considered to be more easily transmitted. They include:

    • 428 cases of the Delta variant, first detected in India;

    • Seven cases of the Alpha variant, first detected in Britain;

    • Nine cases of the Beta variant, first detected in South Africa; and

    • Five cases of the Gamma variant, first detected in Brazil.

    As for imported cases, the Health Ministry said that as at May 31, there were 491 cases infected with variants of concern. They include:

    • 122 cases of the Delta variant;

    • 197 cases of the Alpha variant;

    • 168 cases of the Beta variant; and

    • Four cases of the Gamma variant.

"Studies are ongoing to get a more complete understanding of these variants and we will adjust our strategies as more information is made available."

Singapore has stepped up its testing, contact tracing and vaccination programme to keep the situation under control, the spokesman added.

Genomic sequencing refers to the technique used by public health authorities and researchers to "read" the genetic sequence of a pathogen.

While the genetic code of the pathogen that causes Covid-19 is largely the same, variants will show slight differences in their genetic code.

Since this sequence is unique to each variant, this technique allows the authorities and scientists to identify them.

Associate Professor Raymond Lin, director of the National Public Health Laboratory, said Singapore's sequencing efforts have been focused on helping to determine the chain of transmission leading to clusters of cases.

"By understanding that, we try to interrupt or reduce such transmission," he said.

Dr Sebastian Maurer-Stroh, executive director of the Agency for Science, Technology and Research's Bioinformatics Institute, added that the high frequency of the Delta variant in Singapore is to be expected.

"There was one big cluster of the Delta variant locally, and many regional travellers carry the Delta variant, so the relative frequency is high in Singapore," he said.

In Singapore, the variant surfaced in the two biggest community clusters in recent months - in Changi Airport and TTSH.

Among the seven Delta variant cases reported in Singapore as at May 4, five were part of the TTSH cluster - which had by then grown to include 40 hospital staff, patients and their relatives.

Dr Maurer-Stroh said that relative frequencies in small countries with few cases are often biased towards one variant.

"As clusters are controlled better, the number of cases, and hence genomic sequences, is reduced until only one virus genome is reported," he said.

"A rise in relative frequency accompanied by reduced case numbers in Singapore, which has a strong surveillance system, actually shows success in controlling the virus," he added.

A version of this article appeared in the print edition of The Straits Times on June 10, 2021, with the headline '550 cases of Delta variant in S'pore at end-May'. Subscribe