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More than a third of COVID-19 cases in the U.S. are now caused by the Omicron subvariant BA.2.
Although the proportion of BA.2 cases is increasing, overall infections are still declining from the record highs seen in January, according to Reuters.
For the week ending March 19, BA.2 accounted for 35% of U.S. infections, according to the latest data from the CDC. That compares with 22% a week before, which was revised down from 23%.
The subvariant is more widespread in some parts of the country. In New England, BA.2 now makes up about 55% of new infections, compared with 39% the week before. Around New York and New Jersey, BA.2 accounts for 48% of new cases.
BA.2 cases are surging in parts of Asia and Europe, and public health officials are tracking how the trend may affect the U.S. Cases will likely go up, given previous patterns during the pandemic, Reuters reported, but another wave isn't expected right now.
"Unless something changes dramatically," a major surge isn't on the horizon, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, told The Washington Post on Tuesday.
At the same time, the U.S. will likely see "somewhat of an uptick," Fauci said, as the U.S. generally lags the U.K. by about 3 weeks.
"So if we are going to see an uptick, we should start seeing it within the next week or so," he said.
So far, there doesn't appear to be evidence that the rise of BA.2 is leading to an increase in COVID-19 cases, Daniel Kuritzkes, MD, chief of the Infectious Diseases Division at Brigham and Women's Hospital, told Reuters.
"I think the one concern and where people need to remain vigilant is that, as we have relaxed many restrictions around masking and gathering, there is a potential opportunity for BA.2 or any variant to gain a foothold," he said.
The Institute for Health Metrics and Evaluation at the University of Washington, which has provided COVID-19 projections during the pandemic, also said it doesn't expect a major surge in the U.S. in the coming weeks. The institute released a new projection on Monday, which shows a steady decline in infections through the spring.
"However, it is possible that the rapid return to pre-COVID-19 behavior and the spread of BA.2 could see a short period of increasing case numbers," Ali Mokdad, PhD, an epidemiologist at the institute, wrote in a post on Twitter.
More attention should focus on ensuring that people who have symptoms, especially those in high-risk groups, have access to antiviral treatments, he said.
"Even if the transmission does increase for a period due to reduced mask use and social distancing combined with BA.2, we do not think that implementation of mask or social distancing mandates would be warranted," Mokdad said.
Reuters: "A third of U.S. COVID now caused by Omicron BA.2 as overall cases fall."
CDC: "COVID Data Tracker: Variant Proportions."
The Washington Post: "Transcript: Coronavirus: New Variants with Anthony S. Fauci, MD."
Institute for Health Metrics and Evaluation: "COVID-19 Projections," March 21, 2022.
Twitter: @AliHMokdad, March 22, 2022.
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Cite this: Carolyn Crist. BA.2 Is Behind More Than 1 in 3 COVID Cases in US - Medscape - Mar 23, 2022.