Is the Omicron BA.2 Variant Creeping Up in the U.S.?

BA.2, a subvariant of Omicron, is spreading in parts of Europe and in China. It is also starting to grow in prevalence in the United States, but new cases remain low.

COVID-19 case rates are climbing in the United Kingdom, Denmark, Switzerland, among others. In China, BA.2 may be responsible for the country’s "biggest outbreak in two years," according to NPR.

According to data from the Centers for Disease Control and Prevention (CDC), BA.2 now accounts for about 23% of cases in the U.S.

New York is among the states reporting accelerated growth of BA.2. From February 5 to March 12, the variant claimed up to 23% of the state's cases. But total cases in the state have declined and plateaued.

Experts are cautiously optimistic that BA.2 may not cause a surge in the U.S. due to high levels of vaccinated individuals and people who have developed hybrid immunity. But that doesn't mean that the variant is mild, or that the country should forego all pandemic restrictions.

“I don't think we're out of the woods yet," Andrew Pekosz, PhD, a virologist and researcher at Johns Hopkins Bloomberg School of Public Health, told Verywell. He said Omicron has shown the extremes of how transmissible the virus can be.

U.S. COVID Trends

The U.S. sometimes lags behind the U.K. for about two weeks in terms of COVID-19 surges, but not always. So far, BA.2 is spreading much quicker in the U.K. than in the U.S.

The subvariant has yet to drive a surge in total cases in the U.S., but people who have COVID-19 may be more likely to be infected with the BA.2 variant, Pekosz said.

The World Health Organization (WHO) released a statement in February calling for BA.2 to continue to be monitored as BA.2 has a "growth advantage" over the original Omicron.

Wastewater Surveillance Helps Monitor BA.2

In certain U.S. cities and states, wastewater surveillance has revealed higher levels of BA.2 than test sequencing did. Wastewater surveillance can be an earlier indicator of cases or variant spread because it immediately examines the presence of the COVID-19 virus in the area's population without needing to wait for data collected from PCR tests.

Multiple city and state health systems have set up wastewater surveillance protocols, and the CDC works with the National Wastewater Surveillance System (NWSS) to track the virus through wastewater nationwide.

“Wastewater surveillance is a valuable tool because it can sort of predict trends in cases,” Pavitra Roychoudhury, MSc, PhD, instructor at the department of laboratory medicine and pathology at the University of Washington, told Verywell.

People infected with COVID-19 can shed the virus in their feces even if they have no symptoms. By measuring the virus levels in the sewage system, public health officials can determine if infections are rising in the community, according to the CDC.

Roychoudhury works at a sequencing lab that relies on test results provided by the Washington State Department of Health. As at-home testing becomes more and more popular, labs like her own may be missing chunks of data, she said.

In Washington state, BA.2 appeared to account for about 31% of cases as of March 18.

Steve Balogh, PhD, is a research scientist leading wastewater surveillance in the Twin Cities. His team is working with the University of Minnesota’s Genomics Center to track COVID-19 variants, including BA.2. Balogh told Verywell that wastewater surveillance “provides a comprehensive picture of the prevalence of the virus and viral RNA" in a community and goes beyond what test-based sequencing can offer.

“It doesn't matter if people are symptomatic or asymptomatic, or if they're getting tested or not tested, whether they are seeking health care or not. If they're shedding the virus, it's in the wastewater and we see it,” Balogh said.

In Saint Paul’s wastewater samples, the prevalence of BA.2 has risen from about 3% to 17% of the cases in about five weeks, Balogh said. In a report released on March 17, the Minnesota Department of Health has yet to separate BA.1 and BA.2 in its list of circulating variants.

Another Omicron Takeover?

Both versions of the Omicron variant have been reportedly more transmissible and better at evading vaccine-induced immunity than past strains of COVID-19.

“BA.1 and BA.2 are sort of like siblings,” Pekosz said, noting that almost no other variant remains widely in circulation in the U.S.

Still, the siblings aren’t identical. They differ in some mutations in the genetic sequence, including in their spike proteins, according to the WHO. Such changes in genetic structure could leave room for future mutations if a surge is to follow, Pekosz said. 

“It's good to keep your eye on Omicron," he added. "But I think we also have to keep our eyes wide open and look for the potential emergence of new variants that are unrelated to Omicron."

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