People wearing face masks are seen shopping at a supermarket in Foster City, the United States, April 22, 2020. Masks are required in some Bay Area counties. (Photos: Xinhua)

A woman wearing face mask is seen shopping at a supermarket in Foster City, the United States, April 22, 2020. Masks are required in some Bay Area counties.

A man wearing face mask is seen shopping at a supermarket in Foster City, the United States, April 22, 2020. Masks are required in some Bay Area counties.

A man wearing face mask is seen shopping at a supermarket in Foster City, the United States, April 22, 2020. Masks are required in some Bay Area counties. \