Cook County is now seeing "substantial" community transmission of COVID-19, per data federal health officials updated on Thursday, meaning fully vaccinated people should resume wearing masks indoors under new guidance released earlier this week.
Cook County was added to the list of counties seeing "substantial" transmission Thursday. Other Chicago-area counties in that same category include: Will, DuPage, Kendall, McHenry, Boone, Winnebago, DeKalb, LaSalle and Grundy.
You can find the map of each county in the U.S. and its transmission level here
The Centers for Disease Control and Prevention updated its guidance Tuesday to recommend that fully vaccinated people should wear masks in indoor settings again in areas of the U.S. that are seeing substantial or high transmission of COVID-19.
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The new guidance marked a reversal from earlier recommendations that said fully vaccinated people could remove masks in most settings.
Many of Illinois' counties fall into either "substantial," labeled in orange, or "high" transmission, labeled in red. Some counties - mostly concentrated in the northern and central regions of the state - are seeing "moderate" transmission, labeled in yellow, while just two are colored blue for "low" transmission, with indoor masking recommendations not applying to those two categories.
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.
Chicago's top doctor said earlier Thursday that the city could move into the "substantial" transmission category "very shortly," noting that an average of 200 new cases per day would signal that shift.
"Sitting at 185 average cases per day and increasing, I do anticipate we will be moving very shortly into that substantial risk category," Chicago Department of Public Health Commissioner Allison Arwady said in a Facebook Live Thursday.
Chicago could make formal announcements about further COVID precautions next week, Arwady continued, blaming the delta variant for the increased number of cases in Chicago and across Illinois.
More than 97% of people contracting COVID from the delta variant are unvaccinated, Chicago Mayor Lori Lightfoot said Thursday as she encouraged residents to get the vaccine."Without that protection, you're playing Russian roulette," Lightfoot said. "This variant is real. It is deadly."
The CDC also said Tuesday 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 Tuesday that it is "fully adopting" the CDC's updated guidance.
IDPH also said the state will follow the CDC's new recommendations for K-12 schools, recommending universal masking indoors among teachers, staff, students and visitors to schools, regardless of vaccination status.
"While data continues to show the effectiveness of the three COVID-19 vaccines currently authorized in the U.S., including against the Delta variant, we are still seeing the virus rapidly spread among the unvaccinated," IDPH Director Dr. Ngozi Ezike said in a statement, noting that COVID cases and hospitalizations continue to increase, especially among those who are unvaccinated against the virus.
"The risk is greater for everyone if we do not stop the ongoing spread of the virus and the Delta variant," Ezike said. "We know masking can help prevent transmission of COVID-19 and its variants. Until more people are vaccinated, we join CDC in recommending everyone, regardless of vaccination status, wear a mask indoors in areas of substantial and high transmissions, and in K-12 schools."
IDPH pointed to the CDC's data on the delta variant showing the variant is considerably more contagious than other strains and spreads more than twice as easily from person to person.
Ezike and IDPH continued to encourage Illinois residents to get vaccinated.
"According to CDC, the Delta variant is causing some vaccine breakthrough infections, but even so, most breakthrough infections are mild, and the vaccines are preventing severe illness, hospitalization, and death," IDPH said.
