The World Health Organization said Monday that it is tracking a few dozen cases of two new highly transmissible subvariants of the Omicron variant of the coronavirus to assess whether they are more infectious or dangerous.
WHO added BA.4 and BA.5, sister variants to Omicron’s original BA.1, to its watch list. It is already keeping track of the BA.1 and BA.2 variants – which are now the dominant ones worldwide – as well as BA.1.1 and BA.3.
He said he started following them because of their “additional mutations, which need further study to understand their impact on immune escape potential.”
Viruses mutate all the timebut only a few mutations affect their ability to spread or evade previous immunity from vaccination or infection, or the severity of the disease they cause.
For example, BA.2 now accounts for nearly 94% of all sequenced cases and is more transmissible than its sisters, but the evidence so far suggests that it is no more likely to cause severe disease.
According to WHOonly a few dozen cases of BA.4 and BA.5 have been reported to the global GISAID database.
The UK Health Security Agency said last week that the BA.4 subvariant was detected in South Africa, Denmark, Botswana, Scotland and England between January 10 and March 30.
All cases of BA.5 occurred in South Africa as of last week, but on Monday Botswana’s Ministry of Health said it had identified four cases of BA.4 and BA.5, all of them in people between the ages of 30 and 50 who they were fully vaccinated and experiencing mild symptoms.