Video: Dr. Robert Murphy, professor of infectious diseases and executive director of the Havey Institute for Global Health at Northwestern University's School of Medicine, joins “Chicago Tonight.” (Produced by Andrea Flores)

Chicagoans may once again face a “high” risk of contracting COVID-19, and city officials are warning that a mask advisory may be put back in place as early as this week.

Mayor Lori Lightfoot on Thursday said the city is expected to move from a “medium” risk level for contracting COVID-19 back to a “high” risk level, likely sometime in the next week. When that happens, the city will reinstate an advisory urging Chicagoans to mask up.

“Cases, as many of you have already heard, are on the rise in our city and nationwide and we expect to reach the ‘high’ level soon,” Lightfoot said during a press conference Thursday morning.

When that advisory is back in place, Chicago officials will once again be asking — but not requiring — all residents ages 2 and up to wear masks in indoor public settings.

The Centers for Disease Control and Prevention updates community risk levels weekly on Thursdays. Commissioner of the Chicago Department of Public Health Dr. Allison Arwady said it’s “unlikely” that Chicago and Cook County are moved into the “high” risk category tonight, but she does expect that shift to happen before long.

“I think it’s likely in the very short time period coming here over the holidays,” she said, “which is part of why we wanted to lift up the conversation right now.”

Lightfoot said 43 other counties across Illinois have already moved into the “high” risk level last week.

Since the start of the pandemic, nearly 8,000 Chicagoans have died of COVID-19, according to Arwady. She and Lightfoot repeatedly stressed Thursday the need for all eligible residents to get up to date on their vaccinations and boosters to prevent further spread.

More than 5.6 million COVID-19 vaccinations have been administered to Chicagoans since the vaccines became available, according to Arwady. That includes 500,000 updated bivalent boosters, which represents about 1 in 5 adults and less than 2 in 5 older adults.

“That’s well above national averages, but it’s not enough,” Arwady said.

While the city is averaging less than 1 COVID-19 death per day, Arwady said that unvaccinated residents are three times more likely to be hospitalized and five times more likely to die from the disease than those who have their vaccines.

As of Wednesday evening, Chicago was averaging 643 new COVID-19 cases per day, which is about 4% higher than a week ago, according to data from the CDPH. The number of COVID-19 related hospitalizations is down slightly from last week (42 per day as of Wednesday versus 45 per day last week), but the percentage of hospital beds across the city in use has crept above 5%.

With freezing temperatures and holiday gatherings planned across the city this weekend, officials are expecting to see increases in those figures in the coming days.

“I want people to gather, I want people to have their celebrations,” Arwady said. “(But) doing some of these other things — staying home if you’re sick, testing in advance of gatherings — that can help limit some of that.”

Cook County remains at a medium risk as of Wednesday, with 147 new cases per 100,000 people over the last week and 7% of hospital beds occupied by COVID-19 patients, according to the Cook County Department of Public Health. There have also been 11.1 hospital admissions per 100,000 residents over the last week.

If the number of hospital beds taken up by COVID-19 patients surpasses 10%, Arwady said the city would once again consider a “legal (mask) mandate.”

“But the advisory remains the next step and I hope we never need to do anything further than that and that people would do the right thing while we are at the ‘high’ level,” she said.

Contact Matt Masterson: @ByMattMasterson | [email protected] | (773) 509-5431