Every county in Illinois is seeing "substantial" or "high" community transmission of COVID-19, placing the entire state in the category in which everyone over the age of 2 should resume wearing a mask indoors, regardless of vaccination status, federal health officials say.
The Centers for Disease Control and Prevention updated its guidance late last month to recommend that fully vaccinated people wear masks in indoor settings again in areas of the U.S. that are seeing "substantial" or "high" transmission of COVID-19.
The new guidance marked a reversal from earlier recommendations that said fully vaccinated people could remove masks in most settings.
So in which areas is the CDC advising people wear masks indoors? The agency points to its COVID-19 data tracker showing levels of community transmission, along with other data, for each county in the U.S.
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As of Monday, all 102 counties in Illinois were experiencing either “substantial” or “high” levels of community transmission, triggering the recommendation to mask indoors, regardless of vaccination status.
Ninety-seven counties - including every county in the Chicago area - are seeing "high" transmission while five are in the "substantial" transmission range: Putnam, Lee, Carroll, Jo Daviess and Stark, which was the last county to cross the threshold into the higher transmission levels after remaining in "moderate" transmission through Sunday.
The agency uses two measures to group U.S. counties into the four levels of community transmission: the number of new cases per 100,000 residents and the percent of COVID-19 tests that are positive over the past week.
If a county has reported 50 to 100 cases per 100,000 residents over a seven-day period or has a positivity rate of 8% to 10%, it falls into the "substantial transmission" tier, while those reporting 100 cases or more per 100,000 or have a positivity rate of at least 10% are labeled as "high transmission." Those are the two groups for which the CDC recommends mask-wearing.
The CDC also said last week that fully vaccinated people also "might choose to mask regardless of the level of transmission, particularly if they or someone in their household is immunocompromised or at increased risk for severe disease, or if someone in their household is unvaccinated."
The Illinois Department of Public Health said last month that it was "fully adopting" the CDC's updated guidance and following federal health officials' lead in recommending masking indoors at K-12 schools universally among teachers, staff, students and visitors to schools, regardless of vaccination status.
Then on Aug. 4, Gov. J.B. Pritzker announced a new mask mandate, requiring - rather than recommending - that all students, teachers and staff in K-12 schools wear masks while indoors as officials take steps to try to slow the spread of the more transmissible delta variant.
Pritzker said that the new requirement would take effect immediately, and will also apply to all students and coaches participating in indoor sports and other activities.
On Tuesday, Chicago health officials announced a new indoor mask mandate for all individuals 2 years and older, regardless of vaccination status, beginning Friday, Aug. 20.
Masks will be required in all indoor public settings, including bars, restaurants, gyms and private clubs, the Chicago Department of Public Health said.
Masks can be removed at restaurants, bars and other establishments while customers are eating or drinking, as well as for certain activities like beard shaves and facials, according to CDPH.
The announcement came a day after Chicago surpassed the metric of 400 average new cases of COVID-19 diagnosed per day, a figure that city health officials warned earlier in the pandemic would mark a "line in the sand" to implement more mitigations.