CDC: Omicron subvariant accounts for 23% of new cases; 3 more COVID-19 updates

The omicron subvariant BA.2 now accounts for about 23 percent of new cases, according to the latest estimates from the CDC. 

The estimate is for the week ending March 12. Estimates of BA.2 prevalence suggest the subvariant accounted for 11.6 percent of new cases for the week ending March 5. The latest data indicates the subvariant is most prevalent in HHS Region 2, which includes New Jersey and New York. Its estimated prevalence in that region, which also includes Puerto Rico and the Virgin Islands, is 39 percent. 

"Although the proportion of infections with BA.2 is increasing in the U.S., COVID-19 cases are now declining, so it is likely that absolute numbers of BA.2 infections are not increasing as quickly as they might seem from just looking at the proportion that are BA.2," Deborah Dowell, MD, chief medical officer for the CDC's COVID-19 response, told CBS News. 

Existing data suggests there is no significant difference in disease severity between BA.1 and BA.2, the World Health Organization said in its March 8 weekly epidemiological update on COVID-19. Studies from Qatar also suggest previous infection with omicron may offer protection against reinfection with BA.2. Research on whether the efficacy of vaccines and current therapeutics are affected by the subvariant is ongoing.

Three more COVID-19 updates: 

1. Wastewater surveillance of SARS-CoV-2 RNA levels indicate virus levels are rising at 38 percent of sampling sites in the U.S. that submit data to the CDC. 

"It's too early to know if this current trend will continue or whether we'll see a corresponding increase in reported cases across the country. … We encourage local health officials to monitor their numbers closely and use these data as an early warning sign if wastewater levels continue to increase," Amy Kirby, PhD, head of the CDC's wastewater surveillance program, told Bloomberg

2. COVID-19 cases, deaths and hospitalizations continue to decline in the U.S. The seven-day average for new cases was 32,094 as of March 15, levels not seen since July 2021, data from The New York Times shows. Still, experts are concerned rising figures in Europe, driven at least in part by BA.2, may signal what could play out in the U.S. in coming weeks. 

"Great to see U.S. COVID-19 hospitalizations down to 23,000 and approaching their pandemic low. But indicators from the new wave in Europe and U.S. wastewater surveillance suggest this may be short-lived," Eric Topol, MD, founder and director of the Scripps Research Translational Institute in San Diego, tweeted March 14.

3. Germany, the U.K. and the Netherlands are among European countries beginning to see daily new cases increase, according to Our World in Data. In the U.K., for example, there were about 679 new cases per million people reported on March 8. That figure was about 1,082 as of March 15. Hospitalizations in the U.K. are simultaneously climbing. In addition to BA2, experts point to relaxed mitigation measures and waning immunity from vaccination or piro infection as factors behind Europe's COVID-19 incline.


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