Quick Take:

California is ordering a statewide mask mandate for indoor public spaces to go into effect on Wednesday. The move comes as coronavirus case rates have risen by 50% in the last 2 1/2 weeks.

Faced with rising coronavirus cases, California is ordering a statewide mask mandate for indoor public spaces to go into effect on Wednesday.

The order will affect roughly half the state’s population, including San Diego and Orange counties, the Inland Empire, the Central Valley and rural Northern California. The statewide indoor mask mandate order will last a month and will expire on Jan. 15.

Los Angeles County, Ventura County and most of the San Francisco Bay Area have their own indoor mask mandates that were implemented in the summer.

The move comes as coronavirus case rates have risen by almost 50% in the last 2½ weeks, and COVID-19 hospitalizations are up by nearly 15%. County health officials across the state say they suspect they may be seeing the start of a winter jump in coronavirus cases.

The U.S. Centers for Disease Control and Prevention considers California as having a high level of transmission of the coronavirus, the worst tier in the federal agency’s four-tier scale.

California is also recommending that travelers who return or visit the state get tested within three to five days of their arrival.

California’s announcement came on the same day New York enacted its own statewide mask requirement in indoor public spaces, excepting only settings where everyone inside must be vaccinated. Officials in Britain have also re-ordered an expansion of indoor mask mandates.

The new mask orders arrive as the Omicron variant of the coronavirus — discovered only last month — has spread rapidly around the globe. Britain has recorded its first death of someone infected with Omicron variant.

“Omicron will almost certainly overtake Delta and cause new waves of infection globally,” Dr. Tom Frieden, a former CDC director, tweeted. While there has been some optimism Omicron may cause less severe illness, “this will take time to figure out,” Frieden wrote.

Troublingly, studies of household contacts find that Omicron poses more than double the risk of coronavirus transmission compared to Delta, Frieden said. In Britain, officials expect new Omicron cases to become equal to that of Delta sometime in mid-December, with Omicron cases doubling every two to three days.

In addition, many states elsewhere nationally have been struggling with a winter COVID-19 surge to the still-dominant Delta variant. “We see other states in the United States struggle with overwhelmed hospitals, and a high number of cases,” Dr. Mark Ghaly, the California health and human services secretary, told reporters Monday.

With the more recent coronavirus variants, data suggests that if people do become severely sick, they become sicker sooner, Ghaly said. “So the impact on hospitals might be quicker,” Ghaly said.

Also, there is no expectation that stay-at-home orders will return again this winter, so hospitals will in some ways face some challenges that they didn’t last year.

Ghaly said he’s concerned that hospital capacity is still pressed and challenged, particularly in San Bernardino and Riverside counties, across the Central Valley and in the eastern Sierra and the rural north. A number of hospitals throughout the state are busier than usual for this time of year, where staff are still exhausted from battling a nearly two-year-old historic pandemic, and there’s still plenty of pent-up demand for healthcare needs that were postponed during earlier parts of the pandemic.

The evidence is there that masks still make a difference, Ghaly said. The coronavirus is airborne and can also spread silently from infected, asymptomatic people.

“Even a 10% increase in indoor masking can reduce case transmission significantly,” Ghaly said. “Wearing a mask is going to be one of the most important things to help us get through this period of uncertainty.”

“This is a critical time where we have a tool that we know has worked and can work. We are proactively putting this tool of universal indoor masking in public settings in place to ensure we get through a time of joy and hope without a darker cloud of concern and despair,” Ghaly said. “Californians have done this before. And we of course believe we can do it again.”

Ghaly acknowledged that there may be a number of communities across the state that will not comply with an indoor mask mandate.

“We hope that those are few and far between,” Ghaly said. “In some places, the enforcement is going to be stronger than others. And we are at a point in this pandemic where we are expecting Californians to heed the warning … and make the choice to mask up for the period of time as we learn more about Omicron and get through what was a pretty tough time last year.”

Under the new order to go in effect on Wednesday, California is also tightening rules related to entering large indoor events. Existing rules require patrons age 3 and older of indoor events of 1,000 or more people to show proof of full vaccination or the results of a recent negative test.

For patrons who choose to show a recent negative test, existing rules allow them to show a test as much as 72 hours old; the new rules require patrons to show a more recent test — within two days if it’s a PCR test or one day if it’s a rapid antigen test.

California is approaching a statewide COVID-19 death toll of 75,000. The national death total is nearing 800,000.