SAN FRANCISCO, March 16 (Xinhua) -- Six counties in northern California's Bay Area region, including San Francisco, on Monday announced a public health order requesting residents to stay at home except for essential activities.

The "SHELTER IN PLACE" order, which begins on Tuesday until April 7, is regarded as the strictest measure in the United States since the coronavirus outbreak, according to local media.

The six counties -- San Francisco, Santa Clara, San Mateo, Marin, Contra Costa and Alameda -- are all located in Bay Area region, where more than 300 cases have been reported to date, accounting for over two-thirds of the total in the state of California.

San Francisco Mayor London Breed said the measures are necessary to slow the spread of the virus in the community. "We know these measures will significantly disrupt people's day to day lives, but they are absolutely necessary."

"We all have a responsibility to do our part to protect our neighbors, and slow the spread of this virus by staying at home," she said, adding that all daily necessities are to be met.

The order requests people to maintain at least six feet (1.8 meters) from other individuals, wash hands with soap and water for at least 20 seconds as frequently as possible or using hand sanitizer, cover coughs or sneezes, and avoid shaking hands.

All public and private gatherings are prohibited. All non-essential activities, travels and businesses are banned. Essential government services will remain open, such as transit, police, fire, and healthcare services, as well as essential stores like grocery markets, pharmacies, banks and gas stations, according to the order.