WHO adds two new Omicron sub-variants to watchlist

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 sub-variants BA.1 and BA.2, which are now dominating new COVID-19 cases globally, as well as sub-variants BA.1.1 and BA.3.

The WHO said it has begun 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, some variants affect the ability of these sub-variants to spread or to evade immunity acquired through vaccination or infection, or the severity of 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./.