Covid-19: BA.4 and BA.5, the new Omicron strains closely monitored by the WHO

BA.4 and BA.5, the two new daughter strains of Omicron are now the majority in the provinces of South Africa where they have been detected and they now represent between 60 and 75% of the sequenced cases there.

© NIAID

Text by: RFI Follow

1 min

Should we expect new variants of Covid-19?

The World Health Organization has classified two new daughter strains of Omicron, BA.4 and BA.5 as variants of interest.

It is the South African team already at the origin of the discovery of Omicron which is behind their description.

Advertisement

Read more

It only took four months for the BA.4 and BA.5 strains to become the majority in the provinces of

where they were detected.

They now represent between 60 and 75% of the sequenced cases there, a takeover which was made to the detriment of BA.2, which is still responsible for the bulk of the cases of

in the world.

Are these new strains therefore more effective?

In any case, that is what the team that describes them for the first time believes, but it now remains to be seen why.

Are these strains more contagious?

Less sensitive to immune defenses?

Or maybe the latter are less robust than expected following a recent contamination by BA.2?

As often, only time will provide answers.

The F486 mutation observed in mink farms

However, a few factors prompted the

to follow these two new strains with interest: a series of intriguing mutations, in particular the F486 mutation, already observed in mink farms hit by the epidemic.

It is involved in an immune escape phenomenon.

However, the BA.4 and BA.5 variants are not yet classified as variants of concern by the WHO, but their spread will be monitored very closely.

► 

Newsletter

Receive all the international news directly in your mailbox

I subscribe

Follow all the international news by downloading the RFI application

google-play-badge_FR

• Coronavirus

• Health and medicine

• WHO