Understanding the Omicron BA.5 subvariant

Precautions still in place: A traditional lantern shop displaying a reminder for customers to mask up before entry, in Petaling Street, Kuala Lumpur. — ART CHEN/The Star

PETALING JAYA: Malaysia is seeing a wave of new Covid-19 infections ever since two Omicron sub-lineage variants were first detected in the country last month.

The Omicron BA.5 sub-lineage has been pushing up cases everywhere from the United States to nearby Singapore.

According to the World Health Organisation (WHO) in its weekly epidemiological update on July 6, the BA.5 is present in 83 countries.

“Although BA.4 is also rising globally, the rate of increase is not as high as that of BA.5.

“BA.4 has been detected in 73 countries, and now accounts for 12% of all sequences submitted during week 25 (up from 11% in the previous week).

“BA.4 and BA.5 share similar mutations in SARS-CoV-2 spike but have different mutations in non-spike regions,” it said.

There is no evidence yet regarding any change in severity with BA.4, BA.5 or BA.2.12.1 as compared to BA.2.

However, the rise in the prevalence of these three sub-lineages had coincided with an increase in cases in several WHO regions.

“In some countries, the rise in cases also resulted in a surge in hospitalisation, ICU admissions and deaths,” WHO said.

While studies are still being conducted, early data has shown that the BA.5 could be the most contagious variant so far.

A study in the New England Journal of Medicine, published on July 7, found that the three subvariants substantially “escape” neutralising antibodies from vaccination and infection.

“Moreover, neutralising antibody titers against the BA.4 or BA.5 subvariant and (to a lesser extent) against the BA.2.12.1 subvariant were lower than titers against the BA.1 and BA.2 subvariants, which suggests that the SARS-CoV-2 Omicron variant has continued to evolve with increasing neutralisation escape,” according to the study titled “Neutralisation Escape by SARS-CoV-2 Omicron Subvariants BA.2.12.1, BA.4, and BA.5”.

Reports suggest that the variants’ ability to evade immunity vaccines may cause a surge in infections.

Fever, runny nose, cough, sore throat, headaches, muscle pain and fatigue are some of the symptoms.

Health Minister Khairy Jamaluddin said on Friday that Covid-19 infections could increase, especially those caused by BA.5.

BA.5 was first detected in South Africa in February.

It has since become the dominant variant in driving infections up in the United States and most parts of Europe.

Last week, the Centers for Disease Control and Prevention said that BA.4 and BA.5 were estimated to make up a combined 70.1% of the variants in the United States as of July 2.

In Singapore, its Health Minister Ong Ye Kung said on July 5 that about half of the new cases in the republic were due to the BA.4 and BA.5 subvariants. He estimated that this could go up to 80% this week.