Omicron's 'stealth' subvariant BA.2 could go 'wild' in Europe before going global, top epidemiologist says

LONDON — While war rages in Ukraine, not much attention is being paid to surging Covid-19 cases across Europe that could soon start to filter out to the rest of the world.

The rise in cases across the continent, from the U.K. and France to Italy and Austria, is being driven by several factors: The lifting of most — if not all — Covid restrictions, waning immunity from vaccines and booster shots, and the spread of the more transmissible omicron subvariant, BA.2.

"We all hoped and expected a different turn now at the beginning of spring," Ralf Reintjes, professor of epidemiology at the Hamburg University of Applied Sciences, told CNBC this week.

"But the situation in Europe is a bit bumpy at the moment, and in Germany ... the [case] numbers are at a very, very high level, and they're still increasing and have been increasing for quite some time."

Germany is seeing a surge in cases and has reported daily tallies of new infections of between 200,000 to 300,000 a day in the last week.

Reintjes said that the combination "of everyone thinking and expecting somehow that the pandemic is over now" and the relaxation of what he saw as protective Covid measures gives the BA.2 subvariant "a really good chance to spread extremely wild in many parts of Europe."

"It's difficult to predict but personally I think it's very likely that this is going to continue its tour around the globe as well," he added. "That's what viruses in a pandemic usually do."

"There are also quite a few reports that people who have got an omicron infection, or BA.1 variant, then a few weeks later got BA.2 infection," he noted, adding that there is a good chance that this new variant will spread and act like "some sort of new wave of a new pandemic like seasonal flu."

Public health officials and scientists are closely monitoring BA.2, a subvariant of the already highly transmissible omicron variant, as it is accounting for a growing number of new cases in Europe.

To a somewhat lesser extent it is also accounting for a growing number of infections in the U.S. and Asia.

The subvariant is estimated to be 1½ times more transmissible than omicron and is likely to usurp it as the globally dominant variant.

Initial data has shown that BA.2 is a little more likely to cause infections in household contacts when compared with BA.1. It's not believed currently that the BA.2 variant causes more severe illness or carries an increased the risk of being hospitalized, however further research is needed to confirm this, according to a U.K. parliamentary report published earlier in March.

BA.2 has been described as a "stealth" variant because it has genetic mutations that could make it harder to distinguish from the older delta variant using PCR tests, compared with its original omicron parent, BA.1.

The new subvariant is the latest in a long line to emerge since the pandemic began in China in late 2019. The omicron variant — the most transmissible strain so far — overtook the delta variant, which itself supplanted the alpha variant — and even this was not the original strain of the virus.

The World Health Organization has said it is monitoring BA.2 closely, which it said had now been detected in 106 countries, and has also noted a rise in global cases after a recent lull.

In its latest weekly update published Tuesday, the WHO said that after a consistent decrease since the end of January, the number of new weekly cases rose for a second consecutive week last week, with a 7% increase in the number of infections reported, compared to the previous week.

The WHO also noted that while omicron has a number of sublineages, BA.2 has become the predominant variant in the last 30 days, with 85.96% of the virus sequences submitted to GISAID, the public virus tracking database, being the BA.2 variant.

The WHO noted that weekly data shows that the proportion of BA.2 cases, compared to other sublineages, has increased steadily since the end of 2021, with the subvariant becoming the dominant lineage by week seven of 2022.

"This trend is most pronounced in the South-East Asia Region, followed by the Eastern Mediterranean, African, Western Pacific and European Regions. BA.2 is currently dominant in the Region of the Americas," the WHO said.

In the U.K., the latest available data from the Office of National Statistics, for the week ending March 13, showed that the BA.2 variant is now the most common variant in England, Wales, Northern Ireland and Scotland. In the week that was surveyed, 76.1% of all sequenced Covid-19 infections from the survey were compatible with the BA.2 variant, and 23.9% were compatible with the original omicron strain.

In the U.S., the Centers for Disease Control and Prevention says that BA.2 cases now account for 34.9% of all cases in the U.S. with the subvariant making up over half the number of cases reported in some northeastern states, but it has noted that the overall number of infections is still declining from the record highs seen in January.