The World Health Organisation is investigating two new Omicron sub-variants to assess whether they are more infectious or dangerous than their predecessor.
Both BA.4 and BA.5 have been added to the agency’s monitoring list. The former has already been detected in Scotland and England, with the two countries reporting one case each up to 30 March, according to the UK Health Security Agency (UKHSA)
In a variant report published by the UKHSA last week, health officials said there were “potentially biologically significant mutations” in the two variants.
Globally, only a few dozen cases of BA.4 and BA.5 have been reported to GISAID, a worldwide database that monitors the spread of variants
The WHO said it had begun tracking the two sub-variants because of their “additional mutations that need to be further studied to understand their impact on immune escape potential”.
South Africa and Botswana have both reported cases of BA.4 and BA.5, while Denmark has also detected the former.
The earliest BA.4 sample reported to GISAID was from South Africa, with a sample collection date of 10 January 2022.
However, the accumulation of genomes and geographic spread is more recent, suggesting “that the variant is transmitting successfully”, UKHSA said in its latest report.
Viruses mutate all the time but only some mutations affect their ability to spread or evade prior immunity from vaccination or infection, or the severity of disease they cause.
For instance, BA.2 now represents nearly 94 per cent of all sequenced cases and is more transmissible than its siblings, but the evidence so far suggests it is no more likely to cause severe disease.
