BA. 2, the highly contagious omicron subvariant, is now the dominant COVID-19 strain in the U.S., according to data from the CDC.

Numbers show the subvariant, also known as “stealth omicron,” accounted for nearly 55% of all new COVID-19 infections last week.

BA. 2 accounts for more than 70% of cases in the Northeast.

The South and Mountain West regions of the U.S. are seeing fewer BA. 2 cases.

Stealth omicron is the dominant strain worldwide and has led to higher coronavirus surges in some countries.

The World Health Organization has reported there is no difference in severity between the original omicron variant and BA.2.

However, BA.2 is more difficult to detect in PCR tests.