More than a third of new omicron cases are caused by what is known as “stealth omicron”, but scientists do not know how it will affect the future of the pandemic.
Researchers are slowly elucidating details about this strain, a descendant of omicron known as BA.2, while warily watching its spread.
According to Dr. Wesley Long, a pathologist at Houston Methodist in Texas, “we are keeping an eye on BA.2 because it has done particularly well in parts of Asia, Africa, and Europe.”
More than 80 countries and all 50 U.S. states have been found to have BA.2.
In a recent report, the WHO reported BA.2 was dominant in 18 countries and accounted for approximately 36% of sequenced omicron cases submitted in the most recent week to a publicly available international database where scientists exchange coronavirus data. It’s up from 19% two weeks ago.
According to the Centers for Disease Control and Prevention, BA.2 caused about 4% of COVID cases in the United States during the week ending Feb. 19. Across the country, the percentage was lower in some regions and higher in others – about 7% in New England.
BA.2 has a lot of mutations. The virus has been dubbed “stealth” because it lacks a genetic quirk of the original omicron that allowed health officials to distinguish it from delta using a PCR test. While the test can detect a BA.2 infection, it appears to be a delta infection.
Research suggests BA.2 is more contagious than the original omicron – about 30% more contagious, according to one estimate.
Vaccines can, however, protect people from getting sick. Researchers in the United Kingdom found that both types of omicron are protected by them.
Early studies cited by the WHO suggest that exposure to the original omicron also provides “strong protection” against reinfection with BA.2.
DOES BA.2 MAKE YOU SICKER?
Based on experiments with hamsters, a Japanese lab study suggests it might. Researchers concluded that BA.2 poses a higher risk for global health and suggested its own Greek letter as a designation for globally significant variants of concern. WHO’s technical group decided that BA.2 should remain under the omicron category.
Dr. Eric Topol of Scripps Research Translational Institute says that although the severity experiments were conducted on animals, the findings aren’t to be dismissed. “We should keep an open mind and keep assessing.”
HOW WILL BA.2 AFFECT THE PANDEMIC?
COVID-19 cases are declining worldwide, even in places where BA.2 is prevalent.
According to Louis Mansky, director of the Institute for Molecular Virology at the University of Minnesota, “the timing of the upswings and downswings in cases remains unclear.”
Since BA.2 is spreading in a community with varying levels of immunity from vaccines and previous infections, it is difficult for researchers to predict how much the virus will change caseloads. In some places, BA.2 may not spark new surges but may slow COVID declines.
WHO officials emphasize that the pandemic is not over and urge countries to remain vigilant.