Clues revealed as ‘stealth omicron’ advances
Early research shows mutant spreads faster
The coronavirus mutant widely known as “stealth omicron” is now causing more than a third of new omicron cases around the world, but scientists still don’t know how it could affect the future of the pandemic.
Researchers are slowly revealing clues about the strain, a descendant of omicron known as BA.2, while warily watching it become more prevalent.
“We’re all keeping an eye on BA.2 just because it has done particularly well in some parts of the world,” including portions of Asia, Africa and Europe, said Dr. Wesley Long, a pathologist at Houston Methodist in Texas.
This week, a technical advisory group for the World Health Organization advised public health authorities to monitor it as a distinct omicron strain.
Early research suggests it spreads faster than the original omicron and in rare cases can sicken people even if they have already had an omicron infection. There’s mixed research on whether it causes more severe disease, but vaccines appear just as effective against it.
Worldwide spread
BA.2 has been found in more than 80 countries and all 50 U.S. states.
In a recent report, the WHO said
BA.2 was dominant in 18 countries, and it represented about 36 percent of sequenced omicron cases submitted in the most recent week to a publicly available international database where scientists share coronavirus data. That’s up from 19 percent two weeks earlier.
In the United States, BA.2 caused about 4 percent of COVID cases during the week ending Feb. 19, according to the Centers for Disease Control and Prevention. The percentage was lower in some regions and higher in others — hitting about 7 percent in New England.
What’s known
BA.2 has lots of mutations. It’s been dubbed “stealth” because it lacks a genetic quirk of the original omicron that allowed health officials to rapidly differentiate it from delta using a certain PCR test. So while the test can detect a BA.2 infection, it looks like a delta infection.
Initial research suggests BA.2 is more transmissible than the original omicron — about 30 percent more contagious by one estimate.
But vaccines can protect people from getting sick. U.K. scientists found that shots provide the same level of protection from both types of omicron.
Does BA.2 make you sicker?
A Japanese lab study suggests that it could, based on experiments with hamsters. Researchers concluded that the risk for global health “is potentially higher” from BA.2 and proposed that it be given its own Greek letter — a designation for globally significant “variants of concern.” WHO’S technical group said BA.2 should remain under the omicron umbrella.
Though the severity experiments were conducted in animals, the study is “not something to discount,” said Dr. Eric Topol of Scripps Research Translational Institute. “We should keep an open mind and keep assessing this.”
But scientists are finding something different when they look at people. An initial analysis in Denmark showed no differences in hospitalizations for BA.2 compared with the original omicron. More recently, researchers in South Africa found much the same: a similar risk of hospitalization and severe disease with the original omicron variant and BA.2.
How will BA.2 affect the pandemic?
No one knows for sure.
COVID-19 cases are dropping globally, including in some of the places where BA.2 is prevalent.
“The timing of the upswings and downswings in cases remains unclear,” said Louis Mansky, director of the Institute for Molecular Virology at the University of Minnesota.