The Omicron subvariant BA.5 has surpassed other strains to become the dominant one in the US, according to the United States Centres of Disease Control and Prevention (CDC).
It comes as the US faces the highest community transmission level since February.
One in five Americans are in a county with a high risk of catching the virus and one in three is at medium risk, according to the CDC.
The increased number of cases comes after researchers found that BA.4 and BA.5 are resistant to the immunity brought by prior variants such as BA.1 and BA.2. BA.5 is also more efficiently spreading in human lung cells and more capable of causing severe disease, reserach shows.
BA.5 may also be capable of escaping immunity, says other research.
Specialists, however, continue to strongly recommend staying up to date on vaccination as high levels of immunisation can keep the population away from severe illness.
