Riverside County's pubilc health officer Saturday barred all outside gatherings except for those between family members residing in the same home and ordered anyone leaving home to wear a face covering.
The order comes hours after the county's confirmed COVID-19 cases rose to 665, with the death toll reaching 18.
The ban on gatherings excludes essential businesses, such as healthcare offices, grocery stores and gas stations. However, these businesses must use social-distancing measures to keep clients and customers six feet apart and all employees must wear face coverings, the order states.
Face coverings can be bandanas, scarves, neck gaiters or other clothing that does not have visible holes.
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Additionally, all houses of worship are prohibited from all in-person gatherings, including drive-in religious services.
"While more and more Riverside County residents are getting COVID-19, not everybody's getting the message," said Riverside County public health officer Dr. Cameron Kaiser in a news release. "It started with staying home, social distance and covering your face. But now we change from saying that you should to saying that you must."
Law enforcement agencies throughout the county will enforce the order as they deem necessary, health officials said.
Violators are subject to fines, imprisonment or both, according to the order, which goes into effect midnight Sunday and runs through April 30.
Officials asked residents not to call 911 to report groups of people who are not at an essential business because lines need to be kept open for emergencies.