Surgeon General Vivek Murthy said Sunday that he anticipates more counties around the nation will reinstitute COVID-19 prevention measures, including mask mandates, amid case surges linked to more transmissible variants of the coronavirus.

Murthys warning came just days after Los Angeles County said all residents would be required to wear masks indoors again, regardless of vaccination status, as new infections linked to the delta variant increased in the region. The delta variant is highly transmissible and already accounts for a majority of the new cases in the U.S. Public health officials have warned that unvaccinated Americans are particularly vulnerable.

Its very reasonable for counties to take more mitigation measures like the mask rules you see coming out in LA, and I anticipate that will happen in other parts of the country too, Murthy said during an interview on ABC News This Week.