The World Health Organization reported that the highly contagious Omicron subvariant, BA.2, which is helping to trigger a new wave of coronavirus cases in Europe, is now the dominant version of Omicron around the world.
Globally, BA.2 accounted for about 86 percent of cases reported to WHO between Feb. 16 and March 17, the agency said in a report Tuesday. The previously dominant subvariants, BA.1 and BA.1.1, together accounted for about 13 percent of cases.
BA.2 is already dominant in the WHO’s US region, and cases have been steadily rising in parts of Africa, Asia, Europe and the Middle East since late 2021, the agency said.
When the WHO last reported these numbers on March 8, it said BA.1.1 was the dominant subvariant and BA.2 accounted for 34 percent of new cases.
In the United States, about a third of new coronavirus cases are BA.2, said Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, during a White House briefing Wednesday. US health officials have said they expect the number of cases to rise, but they don’t expect a major increase as a result of BA.2.
Although BA.2 is more transmissible than BA.1, it has not been shown to cause more serious disease. And while the virus has evolved significantly since the first vaccines were developed against it, the inoculations still work, said Dr. Maria Van Kerkhove, the WHO Covid-19 technical leader, in an interview posted on the agency’s website on Tuesday.
“Our vaccines continue to be incredibly effective in preventing serious illness and death, including against both sublines of BA.1 and BA.2,” she said.
Scientists suspect that BA.2’s rapid growth is due to its unique mutations. In the gene for the spike protein on the surface of the virus, BA.2 has eight mutations that are not found in BA.1.
While BA.2 has become the newest subvariant in many people’s minds, there are also three so-called recombinant variants that the WHO deemed remarkable enough to be mentioned. One of these variants, nicknamed “Deltacron”, was discovered in February, but had no official name yet.
On Tuesday, the agency said it had named the three variants — two versions of Deltacron and one that combined BA.1 and BA.2 — XD, XE and XF. There was no evidence that these recombinant variants are more transmissible or cause “serious outcomes,” the report said.
dr. Van Kerkhove said that over the past two years, virus surveillance, testing and sequencing has helped countries implement public health measures that have evolved with the virus.
Her statement came the same day a senior WHO official in Europe said cases in the region have risen as authorities eased pandemic restrictions too quickly.
Rather than take a gradual, deliberate approach, the countries are “brutally lifting those 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 reporting contributed.