As BA.2 grows in the US, experts look to other countries to predict its impact in the U.S.

BA.2 caused about 35% of cases in the US last week, up from 22% the week before, according to new estimates from the United States Centers for Disease Control and Prevention, which were posted on Tuesday.

At the same time, new Covid-19 cases are holding steady or increasing in about 19 states, according to data from Johns Hopkins University.

Some of the states seeing increases—New York, New Hampshire, Massachusetts, Vermont, and New Jersey are in northeastern regions where the CDC estimates that BA.2 is now causing more than half of new Covid-19 cases.

Health officials have warned that overall Covid-19 infections could rise across the US in a few weeks, parallel to trends in the UK and Europe . ...