CHICAGO (CBS) — Chicago is averaging more than 400 new cases of COVID-19 per day, up more than tenfold over the past two months, reaching a point where public health officials have warned the city might be forced to reinstate some virus restrictions.

The latest surge in cases is largely driven by the more contagious delta variant, which is spreading mostly among those who haven’t been fully vaccinated.

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Chicago Department of Public Health Commissioner Dr. Allison Arwady said last week that the delta variant accounts for more than 90% of new cases not only in Chicago, but nationwide. More than 99% of new cases, hospitalizations, and deaths are people who have not been fully vaccinated.

Chicago is averaging 419 new cases of COVID-19 per day over the past week, up from the rate’s lowest point of less than 40 per day in mid-June.

While virus cases have been surging again in recent weeks, vaccinations have started to climb again as well. Chicago is averaging an average of 7,287 doses administered per day over the past week, nearly double the rate of 3,662 per day on July 26, according to the Illinois Department of Public Health.

During the pandemic, Arwady has repeatedly said the 400 daily caseload benchmark is a key factor in determining whether the city will impose any COVID-19 restrictions.

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Arwady is scheduled to hold a briefing on the city’s COVID-19 case data on Tuesday afternoon.

According to the U.S. Centers for Disease Control, virtually all of Illinois, including Chicago, is seeing a high level of transmission of COVID-19, prompting a recommendation that everyone wear masks in public indoor settings, regardless of their vaccination status.

While the Chicago Department of Public Health has yet to reinstate a citywide mask mandate, Arwady has said repeatedly in recent weeks that people who have not been vaccinated should wear masks in public settings.

However, she said last week the city is not yet considering requiring vaccinations for people in public settings such as bars and restaurants, although many businesses in Chicago have begun requiring customers to show proof of vaccination on their own.

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Mayor Lori Lightfoot also has said she expects to announce soon whether city workers will be required to get vaccinated against COVID-19 or face regular testing for the virus, as her administration negotiates with various labor unions on what those rules could look like.

CBS 2 Chicago Staff