The Summit County Public Health Department reinstated its public health order Wednesday, mandating face masks in indoor areas amid a massive COVID-19 surge in the county.

The order will go into effect Thursday and is set to expire Jan. 31, unless the health department extends it. The mask mandate applies to all public indoor spaces, including public facilities, businesses and other common spaces.

“(The decision) was made in response to an alarming increase in COVID-19 cases in the community during the past week as medical providers reported a dramatic spike in the number of sick individuals,” the health department said in a statement.

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On Wednesday, Summit County had the highest COVID-19 incidence rate in the U.S., with 378 cases per 100,000 people, according to data collected by The New York Times. Two other Colorado counties – Pitkin and Eagle – were also in the top five nationally.

The health department said officials believe the county’s spike in COVID-19 cases is due to the rise of the omicron variant in the community and indoor gatherings during the holidays. On Monday, the county issued a public health alert asking residents to wear masks indoors.

Summit County’s new mask mandate comes as Denver and other metro counties extended their mandates Tuesday, citing omicron surges through the metro area and the state.

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On Tuesday, there were 896,403 known cases of COVID-19 in Colorado, the public health order said. In addition, 50,206 Coloradans have been hospitalized with COVID-19 and 10,461 Coloradans have died of COVID-19.

Summit County’s new order also “strongly encourages” COVID-19 vaccinations to be required for attendance to restaurants, bars and indoor events of 500 people or more.

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Businesses that serve vulnerable or at-risk populations like homeless shelters and jails are strongly encouraged to implement a vaccine mandate for employees and/or to require serial testing for unvaccinated employees.

Failure to comply with the order is subject to penalties including a fine of up to $5,000 and up to 18 months in county jail, according to the health department.