Gov. Gavin Newsom pulled what he called an “emergency brake” on Monday, imposing stricter restrictions of businesses in dozens of California counties to try to stem an explosion of coronavirus cases.

Although Los Angeles County was already under the state’s most restrictive rules, Orange County was one of dozens of areas Newsom announced would immediately move backward in the state’s color-coded reopening rules.

Starting Tuesday, Orange County and dozens of other counties were bumped back to the strictest “purple” tier that bans indoor dining, most in-person school classes and other higher-risk activities.

Newsom said the state was taking emergency measures because the number of new daily cases across the state have doubled in the last 10 days.

“We are sounding the alarm,” Newsom said in a statement. “California is experiencing the fastest increase in cases we have seen yet—faster than what we experienced at the outset of the pandemic or even this summer. The spread of COVID-19, if left unchecked, could quickly overwhelm our health care system and lead to catastrophic outcomes.”

The troubling rise in cases this month has come at a faster pace than a spike in mid-June and could quickly surpass the peak of the hospitalizations at the time, health officials said. The state became the second in the U.S. last week to surpass 1 million cases of the virus.

Just like the rest of the state, cases are surging in LA County, which saw 3,000+ new infections for two straight days over the weekend. That’s more than three times what the county’s average daily case rate was in early October.

The measures that Newsom said were the “emergency brake” will impose more restrictions on businesses across most of the state. With the announcement, 41 of California’s 58 counties are now in the most restrictive tier.

Newsom also said state officials are also considering the idea of a curfew for certain industries or businesses, but they’re still studying the issue.

The new rules are certain to rankle business owners such as restaurateurs and gym owners who have been struggling to get back on their feet after lengthy shutdowns followed by reopenings that have at times been curtailed as cases have risen.

Businesses have complained that they have played by the rules yet have had to pay the price for residents who didn’t do so. Newsom himself has faced blowback after failing to follow his own rules by attending a friend’s birthday party at the opulent French Laundry restaurant in wine country north of San Francisco.

The state has blamed the spike in cases mainly on people who have grown fatigued coping with the virus and have ignored public health warnings to not socialize with friends and family members. Those warnings have been more forceful in advance of Thanksgiving next week.

Newsom and the governors of Oregon and Washington on Friday issued a travel advisory urging their residents to avoid non-essential travel and to quarantine for two weeks after arriving on the West Coast from another state or country.

Dr. Mark Ghaly, state Secretary of Health and Human Services, urged people to avoid gathering indoors with other households.

“We must keep transmission low, and that’s to avoid flooding the healthcare delivery system,” he said.

Newsom also said the state has 11 “surge facilities” that can be activated to prevent hospitals from being overwhelmed in particularly hard-hit areas. He said the first such facility will be activated in Imperial County.

Newsom’s announcement Tuesday also puts in some structural changes for the state’s color-coded reopening tiers.

Previously, counties could only move backward in the roadmap if they failed to meet key metrics—the rates of new cases and positive tests—for two consecutive weeks. Now a county will be moved backward after just one week of elevated numbers.

Counties can also potentially be moved back multiple tiers in the matrix if the numbers warrant, Newsom said. Under the new guidelines, counties that are moved backward in the tier system must require businesses to meet the accompanying restrictions immediately, as opposed to a previous three-day grace period.

The state previously updated counties’ placement in the matrix once a week—every Tuesday—but now counties can be moved at any time based on the numbers, the governor said.

Staff writer Jeremiah Dobruck, City News Service and Associated Press writers Adam Beam and Brian Melley contributed to this report.