The World Health Organization announced Monday that it is monitoring several dozen cases of two new subtypes of the highly contagious coronavirus strain Omicron to assess whether they are more contagious or dangerous. It has added BA.4 and BA.5, sister variants of the original BA.1 Omicron variant, to its watchlist. It already tracks BA.1 and BA.2 – now globally dominant – as well as BA.1.1 and BA.3. The WHO said it had begun monitoring them because of “additional mutations that need to be further studied to understand their impact on the immune system’s escape potential”. Viruses are constantly mutating, but only certain mutations affect their ability to spread or prevent previous immunity from vaccination or infection or the severity of the disease they cause. For example, BA.2 now accounts for almost 94% of all sequence cases and is more contagious than its siblings, but evidence to date suggests it is less likely to cause serious illness. Only a few dozen cases of BA.4 and BA.5 have been reported in the global GISAID database, according to the WHO. The UK Health and Safety Administration said last week that BA.4 had been found in South Africa, Denmark, Botswana, Scotland and England from January 10 to March 30. All BA.5 cases have been in South Africa since last week, but on Monday the Botswana Ministry of Health said it had identified four cases of BA.4 and BA.5, all between 30 and 50-year-olds who had been fully vaccinated and showed mild symptoms. Our Morning and Afternoon Newsletters are compiled by Globe editors, giving you a brief overview of the day’s most important headlines. Register today.
