The World Health Organization has reported that the highly contagious Omicron subvariant, BA.2, which is helping to drive a new wave of coronavirus cases in Europe, is now the dominant version of Omicron worldwide.
Globally, BA.2 accounted for about 86% of cases reported to the WHO between February 16 and March 17, the agency said in a statement. report Tuesday. The previously dominant subvariants, BA.1 and BA.1.1, together accounted for approximately 13% of cases.
BA.2 is already dominant in the WHO Region of the Americas and its share of cases has been steadily increasing in parts of Africa, Asia, Europe and the Middle East since the end of 2021, the agency said.
When the WHO lasted reported these numbers, on March 8, he said BA.1.1 was the dominant subvariant and BA.2 accounted for 34% of new cases.
In the United States, about a third of new coronavirus cases are BA.2, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said in a White House briefing on Wednesday. US health officials said they expected an increase in cases, but did not foresee a major increase caused by BA.2.
Although BA.2 is more transmissible than BA.1, it has not been shown to cause more severe disease. And even though the virus has evolved considerably since vaccines against it were first developed, inoculations still work, Dr Maria Van Kerkhove, WHO technical lead for Covid-19, said in a statement. . maintenance posted on the agency’s website on Tuesday.
“Our vaccines remain incredibly effective in preventing serious disease and death, including against both BA.1 and BA.2 sublines,” she said.
Scientists suspect that the rapid growth of BA.2 is due to its unique mutations. In the spike protein gene on the surface of the virus, BA.2 a eight mutations not found in BA.1.
Although BA.2 has become the last sub-variant in many people’s minds, there are also three so-called recombinant variants that the WHO has deemed remarkable enough to name. One of these variants, dubbed “Deltacron”, was discovered in February but had not been officially named.
On Tuesday, the agency said it had named the three variants – two versions of Deltacron and one combining BA.1 and BA.2 – XD, XE and XF. There was no evidence that these recombinant variants were more transmissible or caused “more severe outcomes”, the report said.
Dr Van Kerkhove said that over the past two years, surveillance, testing and sequencing of the virus have helped countries implement public health measures that have evolved with the virus.
His statement came the same day a senior WHO official in Europe said cases had risen in the region because authorities had been too quick to ease pandemic restrictions.
Rather than taking a gradual and measured approach, countries are “suddenly lifting these restrictions, from too much to too little”, said the official, Dr Hans Kluge, the organization’s regional director for Europe.
Dr Kluge added that the increase in new cases was linked to the spread of BA.2.
Sheryl Gay Stolberg and Matthew Mpoke Bigg contributed report.