Nevada is reinstating a coronavirus mask mandate requiring people in high-transmission areas to wear masks in public indoor spaces – regardless of vaccination status.

The mandate becomes effective at 12:01 a.m. Friday in 12 of 17 counties in Nevada, according to state health officials on Tuesday. 

"Businesses and residents in counties with substantial or high transmission are strongly urged to adopt the changes as soon as possible," officials said in a statement.

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The mandate follows guidance from the Centers for Disease Control and Prevention (CDC), which earlier in the day urged fully vaccinated Americans to wear masks indoors in areas with high transmission. In May, Gov. Steve Sisolak signed an emergency directive to automatically adopt CDC guidance on mask-wearing, FOX 5 Vegas reported.

Las Vegas, Carson City, and Reno are among the cities the indoor mask requirement applies to. The Nevada Gaming Control Board noted the mandate would also apply to casinos in counties with high transmission rates.

Crowds walk through the casino during the opening night of Resorts World Las Vegas in Las Vegas on June 24, 2021.  (AP Photo/John Locher, File)

Crowds walk through the casino during the opening night of Resorts World Las Vegas in Las Vegas on June 24, 2021.  (AP Photo/John Locher, File)

In Nevada, and throughout the U.S., the highly contagious Delta variant continues to fuel a recent spike in cases. As of Tuesday, at least 1,143 people in the state were hospitalized, according to state data. 

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"This update comes as the Delta variant now accounts for the majority of new cases," the statement added. "The Delta variant has shown to be much more contagious and spreads more than twice as easily from one person to another, compared with earlier strains."

Most new infections continue to be among unvaccinated people. Breakthrough cases have occurred, but they generally cause milder illness.

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Sisolak’s directive instructs officials to adopt new CDC mask guidelines for students and teachers, though officials said Tuesday that they intend to have "continued conversations" with school officials about recommendations and implementation.

Reno officials added that they plan on requiring masks at their facilities – including city hall and indoor pools – starting Wednesday.

The Associated Press contributed to this report