COVID-19 cases and deaths have been falling across the U.S. for several weeks as the omicron wave recedes. But the Centers for Disease Control and Prevention says a new subvariant of omicron is beginning to spread — BA.2, also known as "stealth omicron."
The CDC said Tuesday that the BA.2 subvariant now represents 23% of newly-reported COVID-19 cases across the country. The subvariant is also spreading rapidly in China — where officials are re-instituting lockdown measures — and in Europe, where some countries are seeing a second omicron wave.
So, what is "stealth omicron," and how is it different? And will it lead to another wave of cases in the U.S.?
What is stealth omicron?
According to the American Medical Association, BA.2 is a subvariant of the omicron variant of COVID-19. Scientists have referred to it as "stealth" omicron because it has "genetic mutations that could make it harder to distinguish from the delta variant using PCR tests as compared to the original version of omicron."
Why are scientists concerned?
Omicron itself is already more contagious than previous variant strains of COVID-19. However, the American Medical Association says that BA.2 is 1.5 times more infectious than the original omicron strain.
Does stealth omicron cause more severe disease?
There's conflicting research. According to ABC News, a study conducted by Japanese scientists studied the effects of BA.2 on hamsters and found the subvariant caused more severe infections than omicron. However, two separate studies from Denmark and South Africa showed that BA.2 presented similar risks for hospitalizations compared to the original omicron strain.
Do vaccines work against stealth omicron?
All indications indicate that COVID-19 vaccines are still effective against BA.2, particularly against severe disease and death, according to Vox.
Will there be another surge in cases?
Scientists are holding out hope that the U.S. will be spared from another omicron surge. They hope that the millions of Americans who had an omicron infection in recent months will have some protection against BA.2 and that immunity levels will only rise as more people seek out vaccines and boosters.
But other countries are seeing a resurgence in COVID-19, particularly in China, which is seeing its biggest outbreak since the virus first emerged in Wuhan. CNBC reports that COVID-19 cases are also on the rise in France, Switzerland, Italy and the Netherlands.
But even as "stealth omicron" is becoming more prevalent in the U.S., case rates, hospitalizations and deaths are still falling.
"Although BA.2 does seem to be growing as a proportion of sub-lineages in the United States, it's not nearly as quickly as we've seen in some other countries. The doubling time in the United States actually seems to be slowing down," Dr. Deborah Dowell, the CDC's chief medical officer for the agency's COVID-19 response, said Tuesday, according to CBS News.