The Omicron surge seems to be slowing in much of the world, but a subvariant that scientists believe is even more contagious is on the rise, and a decline in testing has muddled the global picture, the World Health Organization said.
New cases worldwide dropped 19 percent from Feb. 7 to Feb. 13, compared with the week before, according to the agency.
The W.H.O. also said that the subvariant of Omicron, BA.2, appeared to be “steadily increasing” in prevalence and that BA.2 had now become dominant in several Asian countries, including China, India, Pakistan, Bangladesh and the Philippines. Denmark was the first nation to report that BA.2 had overtaken BA.1, the version of Omicron that first swept through the world.
Scientists have said there is no evidence that BA.2 is more lethal than BA.1, though BA.2 could slow Omicron’s decline. So far, vaccines appear to be just as effective against BA.2 as they are against other forms of Omicron.
The Omicron wave has yet to crest in what the agency calls the Western Pacific region, which includes Oceania, the Pacific islands and East Asian countries like China and South Korea that recently celebrated the Lunar New Year, a holiday period that typically involves large family gatherings. Cases in the region rose 19 percent last week, the W.H.O. reported.
In the Pacific, two island nations that had no confirmed cases until recently are now grappling with the arrival of the virus. In Tonga, an outbreak began after ships brought aid to help the country recover from a volcanic eruption and tsunami in January. And the Cook Islands reported its first case last week.
The W.H.O. said caseloads were falling in the other regions. But cases are still rising in parts of Europe, including in Slovakia, Latvia and Belarus. And in Russia, new cases have increased by 79 percent over the past two weeks, according to the Center for Systems Science and Engineering at Johns Hopkins University.
On Wednesday, Maria Van Kerkhove, the W.H.O.’s Covid-19 technical lead, cautioned that a drop in testing rates around the world has meant the reported global case numbers might not reflect the true spread of the virus.
“We need to be careful about interpreting too much this downward trend,” she said. She said the bigger concern was the increase in reported deaths from Covid-19 for the sixth week in a row.