While BA.2, or “stealth omicron,” remains the dominant omicron subvariant circulating, cases of BA.2.12.1 are substantially increasing, up from 33% of coronavirus cases two weeks ago to nearly 43% of infections last week, according to CDC data published Tuesday.
And in some areas, BA.2.12.1 has already become the dominant subvariant. In the CDC region that includes New York and New Jersey, the strain is responsible for 66% of cases. New York state first sounded the alarm over BA.2.12.1 in mid-April.
Experts believe BA.2.12.1 to be about 25% more transmissible than BA.2, so it is likely contributing to the increase in coronavirus cases seen nationally.
The U.S. is averaging over 66,000 new cases of the coronavirus each day, which is up from a daily average of 29,000 a month ago.
Despite increasing infections, states and cities have not reimplemented mitigation measures like mask-wearing. Hospitalizations due to COVID-19 have also been increasing over the past month, while average deaths seem to be holding steady at over 300 per day.
Experts don’t expect BA.2.12.1 to be any more severe than BA.2, though studies are ongoing.
“Additional evaluation is currently underway to understand the impact of BA.2.12.1 on vaccine effectiveness,” CDC Director Rochelle Walensky recently said. “But importantly, we continue to believe that those who are vaccinated and especially those who are boosted, continue to have strong protection against severe disease, even from BA.2.12.1.”
Other highly transmissible omicron subvariants circulating globally haven’t yet made inroads in the U.S., including BA.4 and BA.5, which have caused an increase in coronavirus cases in South Africa.
While that may sound like good news, for now, it is unclear how those subvariants will spread in the future.
“Many countries have had different types of circulation of different sublineages,” Maria Van Kerkhove of the World Health Organization said at a briefing on Tuesday. “What we don’t quite know yet is what will happen in countries that have a substantial wave of BA.2. Will they see the same growth advantage we see in increasing cases of BA.4 and BA.5?”