As the United States enters the thick of respiratory virus season, COVID-19 variants continue to circulate and sicken Americans. Currently, the dominant strain in the U.S. is a highly contagious omicron subvariant called HV.1, responsible for an estimated one-third of cases nationwide.

Scientists have been closely monitoring HV.1 since it was first reported in the U.S. in late summer. It rapidly overtook other variants, including EG.5 (Eris), becoming the most prevalent strain in October and November, according to the U.S. Centers for Disease control and Prevention.

During a two-week period ending on Dec. 9, HV.1 accounted for nearly 30% of new covid-19 infections in the U.S., as reported by the CDC. The next most common variant was JN.1, a new offshoot of BA.2.86 (Pirola), making up 21% of cases, followed by EG.5. HV.1, unlike its predecessors, has yet to gain a catchy nickname.

The emergence of HV.1 highlights how the SARS-CoV-2 virus, causing COVID-19, can mutate and give rise to new, highly contagious variants.

Experts state that the updated COVID-19 vaccines, rolled out in September, still offer protection against newer variants, including HV.1. However, vaccination rates remain low among eligible Americans.

Health officials are closely monitoring HV.1, but low levels of testing have made it challenging to accurately track new variants. As infections are expected to rise this winter, testing and early detection remain crucial.

As the winter and holiday season approaches, it's important to take steps to protect yourself from COVID-19 and prevent transmission to others, especially the most vulnerable. These include staying up to date with COVID-19 vaccines, getting tested if you have symptoms, isolating if you test positive, and following recommended preventive measures.

CORRECTION (Nov. 27, 2023, 10:30 a.m. ET): A previous version of this story incorrectly stated that insurance companies are still required to reimburse the cost of eight at-home COVID-19 tests monthly. When the federal emergency for the pandemic ended in May 2023, insurance companies were no longer required to do so. But some insurers are still reimbursing the cost of tests. Check your plan for more information.