WHO adds two new sub-variants of Omicron to watch list

The World Health Organization (WHO) announced on April 11 that it is monitoring a number of cases of two new sub-variants of the fast-spreading Omicron variant to see if these sub-variants are more contagious or dangerous.

Specifically, WHO has added BA.4 and BA.5, "sister" variants of the original Omicron sub-variant BA.1, to the list of variants to watch.

WHO has been monitoring the BA.1 and BA.2 sub-variants, which now dominate new COVID-19 cases globally, as well as the BA.1.1 and BA.3 sub-variants.

The WHO said it has started monitoring these sub-variants because "these new mutations need to be studied further to understand their impact on immune evasion".

All viruses change over time. However, only some variants affect the ability of a virus to spread or evade immunity acquired through vaccination or infection, or the severity of the disease caused by these sub-variants.

For example, the BA.2 sub-variant ofOmicron(also known as the stealth Omicron variant) now causes nearly 94% of sequenced cases.

This variant is more transmissible than other sub-variants, but evidence so far suggests BA.2 is unlikely to cause severe disease.

Illustration of sub-lines of the Omicron variant that causes COVID-19. Photo: News-medical.net/TTXVN

According to WHO, only a few cases of BA.4 and BA.5 sub-variants have been reported to WHO's GISAID global database.

The UK's Health Security Agency said last week that the BA.4 sub-variant had been detected in South Africa, Denmark, Botswana, Scotland and England between January 10 and March 30.

Meanwhile, all cases of the BA.5 sub-variant were detected in South Africa until last week.

Botswana's Ministry of Health announced on April 11 that the country had detected four cases of BA.4 and BA.5 sub-variants in people aged 30-50 who were fully vaccinated and had mild symptoms./.