The county, home to 10 million people and the nation's second-largest city, Los Angeles, is one of several jurisdictions to recommend or mandate wearing masks or other pandemic restrictions in recent days as cases rise to worrisome levels in many parts of the United States.
"We’re requiring masking for everyone while indoors at public settings & businesses, regardless of vaccination status so that we can stop the increased level of transmission we're seeing," the Los Angeles County Department of Public Health said on Twitter Thursday.
The mandate will go into effect Saturday night at a minute before midnight, the agency said.
The announcement follows six straight days of more than 1,000 new COVID-19 cases reported in Los Angeles County, with nearly 400 people hospitalized with COVID-19 as of Wednesday, up 275 from the week before. Nine new COVID-19 deaths were reported on Wednesday.
More than 1,500 new infections were reported on Thursday, and the county has become a place of "substantial" transmission, based on criteria set by the U.S. Centers for Disease Control and Prevention (CDC), the Los Angeles County health officer, Dr. Muntu Davis, said in remarks provided to reporters.
Other California counties and other states are also grappling with a spike in coronavirus cases, led by a mutation of the coronavirus known as the Delta variant and predominantly affecting people who are unvaccinated.
Also on Thursday, Sacramento and Fresno Counties in California recommended that masks be worn indoors even by people who are vaccinated. Austin, Texas, on Thursday urged people who are not vaccinated or are otherwise high-risk to avoid travel, indoor gatherings, dining out and shopping, and to wear masks.
Earlier this week, Yolo County in California also recommended indoor masking, and in Springfield, Missouri, children and teachers have been required to wear masks during summer school.
"Everyone, including those who are vaccinated, should be aware of high-risk situations including being indoors, in crowds, and around unvaccinated and unmasked individuals and consider wearing a face covering in these settings,” said Fresno County Public Health physician Dr. John Zweifler.
Data from the CDC high levels of coronavirus transmission in numerous states, including Missouri, Mississippi, Florida, Nevada and Utah.
Across the country, health officials urged residents who have not yet done so to become vaccinated. Vaccines are approved and available for all people as young as 12 years old. In Los Angeles County, just 0.09% of new cases were among people who had been vaccinated, officials said.
“Our best protection against COVID-19 continues to be the vaccine," said Sacramento County Public Health Officer Olivia Kasirye. "We urge all eligible residents to get vaccinated in order to protect themselves, and their family and friends.” Reporting by Sharon Bernstein in Sacramento, California; Additional reporting by Steve Gorman in Los Angeles; Editing by Aurora Ellis and Leslie Adler