Omicron subvariants BA.4 and BA.5 are circulating at low levels in several countries in southern Africa and Europe, according to the World Health Organization.
The two sub-variants of the highly contagious Covid-19 strain have been discovered in Botswana, South Africa, Germany and Denmark, among others, said WHO’s technical manager on Covid-19, Maria Van Kerkhove on Thursday.
BA.4 and BA.5 do not appear to be more contagious or fatal than the original omicron mutation so far, but that may change as more cases are discovered, she added. Van Kerkhove stressed the need to maintain “robust” genome monitoring systems that will allow countries to track and analyze the two sub-variants as well as earlier versions of omicron.
“It’s still early days. What we need to make sure is that we continue to have the ability to track, the ability to share and the ability to analyze so we can answer questions like this,” Van Kerkhove said during a WHO -briefing that was livestreamed on the organization’s social media platforms.
Her remarks come a few days after the WHO said it tracked a few dozen cases of BA.4 and BA.5, in addition to previous omicron variants such as BA.1, BA.2, BA.3 and BA.1.1.
New wave of cases
It also comes as the more infectious BA.2 subvariant evolves across more parts of the world, fueling a new wave of Covid cases following the unprecedented rise caused by the original omicron variant, BA.1, during the winter. BA.2 is now the dominant tribe globally. In the United States, it accounts for about 85% of sequenced new cases and is even more dominant in the northeastern region of the country, where it represents about 92% of recently sequenced cases, according to data from the Centers for Disease Control and Prevention.
The earliest BA.4 sample was collected in South Africa on January 10, but data show that the “accumulation of genomes” and geographical spread of the subvariant are more recent, according to a report by the UK’s Health Security Agency released last week. On April 8, South Africa had reported 41 BA.4 cases, Denmark reported three cases, Botswana reported two and England, as well as Scotland, each reported one.
“Although the number of total genomes is small, the apparent geographical spread suggests that the variant transmits successfully,” the UK Ministry of Health said in a report.
The report also said that there were 27 reported sequences of BA.5 per April 8, all of which were reported in South Africa between February 25 and March 25. But Botswana’s health ministry said on Monday it had identified both BA.4 and BA. 5 cases among fully vaccinated people aged 30 to 50, Reuters reported.
The WHO began tracking BA.4 and BA.5 because they have new mutations, “which need to be further investigated to understand their impact on the immune flight potential,” according to Reuters.
Both subvariants have additional mutations in the spike region, part of the virus used to invade human cells, and unique mutations outside that region, according to a WHO report published Wednesday. Such mutations are associated with “potential immune escape properties,” the report said.
Another omicron subvariant scientists call XE is also circulating at low levels in a number of countries.
XE is a “recombinant” variant that occurs when someone is infected with more than one strain, which is then combined into a new variant. In the case of XE, it is a combination of the original omicron BA.1 strain and the newer BA.2 according to Van Kerkhove.
“We have not seen a change in severity,” she said, meaning it is no more deadly than previous strains.
However, the report from the UK Ministry of Health said that the latest data indicate that XE may be more contagious.
However, it noted that the estimate has not remained consistent as new data are added, meaning that “it can not yet be interpreted as an estimate of growth benefit for the recombinant.”
The earliest confirmed case of XE has a trial date of January 19 and has been detected in the UK, Thailand, India, Israel and most recently Japan. The United States has not yet reported a case of the subvariant.
Cases of the new strain have almost doubled in the UK, according to the latest data from the UK Health Safety Agency. About 1,125 cases of XE have been identified on April 5, an increase from 637 cases on March 25.
CNBCs Spencer Kimball and Karen Gilchrist contributed to this report.