The number of new Covid-19 cases in Missoula County have returned to levels not seen since spring as infections surge across Montana and the rest of the nation.

The rise in new cases, coupled with lagging vaccination rates, prompted the Centers of Disease Control and Prevention on Tuesday to issue new guidance saying people should wear masks when indoors, whether vaccinated or not.

The guidance includes areas with high or substantial transmission rates. The CDC defines “high” as 50 to 100 cases per 100,000 people and “substantial” as more than 100 cases.

The Missoula City-County Health Department on Tuesday said there are 100 active cases in the county, but only 12 new cases per 100,000 people.

Still, Missoula hasn't seen such numbers since early April, according to the department. Local health officials are urging residents to follow the CDC's new guidance on wearing masks.

“Every layer of protection counts right now and dusting those masks off is a wise choice,” said health officer D'Shane Barnett. “With the highly transmissible Delta variant present in our community, those who are old enough to get vaccinated should do so immediately.”

The CDC on Tuesday said new data shows “rare occurrences” in which some vaccinated people who are infected with the Delta variant may be contagious to others.

The local health department last week confirmed the presence of the Delta variant in Missoula. Roughly half, or 53% of county residents, have been vaccinated.

“We are at a critical point where those who have been delaying their vaccines, those who have been hesitating, need to step forward and protect themselves and our community,” said Missoula's Covid incident commander Cindy Farr. “We have come too far to slide back now.”

The CDC's new guidance marks a reversal from its recommendation in May that vaccinated Americans could stop wearing masks in most places. Since then, the Delta variant has become the dominant Covid strain.

Sen. Steve Daines on Tuesday weighed in on the CDC's new recommendation, saying it could undermine confidence in the vaccine.

“COVID-19 vaccines are safe, effective and FREE, and I continue to encourage all Montanans to get vaccinated to help put this pandemic behind us for good,” Daines said in a statement. “With that said, I do not support mask mandates and believe the CDC’s new guidance for vaccinated individuals to wear masks indoors will undermine confidence in vaccines. I believe Montanans understand commonsense, personal responsibility, and think we should continue to move forward, not backwards.”

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