Oakland and Macomb residents among counties that CDC recommends masks indoors

Nearly half of Michigan residents live in counties where the federal government is urging the fully vaccinated to wear masks in public indoor settings because transmission of the coronavirus is "high" or "substantial."

The guidance affected 31 counties as of Monday -- including large ones such as Oakland, Macomb, and Ingham -- up from 10 mostly small, rural counties when the Centers for Disease Control and Prevention's recommendations were issued nearly a week ago. 

The counties are home to more than 4.5 million residents, 46% of the state's population.

Michigan's seven-day average of new COVID-19 cases was 678 on Saturday, an increase from 241 two weeks before. 

The case rate, 76.8 per 100,000 people, was lower than in all but four states, based on data compiled by Johns Hopkins University.

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Gov. Gretchen Whitmer does not plan to reinstate a mask requirement but has urged people to get vaccinated and wear a face covering when inside and among groups. 

Nearly 57% of residents ages 12 and up are fully vaccinated, which is shy of the national average of 58%. 

Michigan's vaccine rate ranks around the middle of the pack among states.