CHICAGO (CBS) — With new COVID-19 cases on the rise again in Chicago, Mayor Lori Lightfoot warned on Monday that the city might have to tighten coronavirus restrictions if the troubling uptick continues.

Even as more people are getting vaccinated at places like the United Center, COVID-19 is still here, and the upward trend in cases the past couple weeks is proof of that.

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“COVID-19 is still here. It is still killing people in our city every single day. So we have got to remain diligent,” Lightfoot said Monday as the city expanded vaccine eligibility to adults with underlying health conditions and all essential workers.

Lightfoot said the recent uptick is driven by adults ages 18 to 39 years old on the North and Northwest Sides.

“We’ve also seen a number of outbreaks involving younger people; among sports teams and as a result of bar crawls,” she said.

The mayor said the activities and locations themselves aren’t the problem, it’s the risky behavior involved, such as not wearing masks or observing social distancing.

The consequences are in the numbers. Chicago is averaging 473 new cases per day, up 34% from last week’s average of 352 cases per day, and a 67% increase over two weeks ago, when the city was averaging 283 new cases per day.

The city’s average test positivity rate is 4.2%, up from 3.2% one week ago, and 2.9% two weeks ago.

“It was about three weeks ago that we were on a downward trend, and we were seeing daily case rates in the 200s. Today, we’re over 400 average new cases a day. And our percent positivity, which was the lowest that it had ever been in the pandemic, in the 2s, is now back to 4%, positivity. This is obviously a very troubling trend,” Lightfoot said.

It’s not just the city. Suburban Cook County is seeing an average of 421 new cases a day and a 4.7% test positivity rate as of Saturday, compared to 296 cases per day and a 3.5% positivity rate two weeks ago.

All of this has happening as more people are becoming eligible for the COVID-19 vaccine, and as more vaccination sites are cropping up.

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In Chicago for example, about 84% of adults are now eligible to get the shot, but officials say vaccinations and mitigation efforts should go hand in hand.

“We don’t want to be forced to take any steps back, or worse close things down because we haven’t done what is necessary now to remain diligent,” Lightfoot said.

So what about the entire state? The number of daily infections and hospitalizations both have grown by double digits over the past week.

Over the past week, Illinois is averaging 2,358 new coronavirus cases per day, an increase of more than 27% over one week ago, when the state was averaging 1,853 daily infections.

As of Sunday night, 1,352 coronavirus patients were hospitalized in Illinois, including 280 in the ICU and 128 on ventilators. Illinois is averaging 1,301 hospitalizations per day over the past week, up more than 13% from an average of 1,149 daily hospitalizations one week ago.

The statewide 7-day average case positivity rate is up to 3.3%, the highest it’s been since Feb. 11. One week ago, the case positivity rate was 2.6%, and it was as low as 2.1% on March 13.

Cases are also climbing nationally, up 10% over the past week. Hospitalizations nationwide also are on the rise.

Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), issued a dire warning of a sense of “impending doom” as coronavirus infections and hospitalizations tick up and pleaded with Americans to not let up on mitigation measures.

“I’m speaking today not necessarily as your CDC director, and not only as your CDC director, but as a wife, as a mother, as a daughter, to ask you to just please hold on a little while longer,” she said Monday.

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Walensky said she fears the U.S. will follow the trajectory in Europe, where cases are spiking and some hospitals are again overwhelmed.