The city of Chicago is allowing bars, restaurants and other venues the ability to increase outdoor capacity while keeping indoor limits at current levels, all while Mayor Lori Lightfoot on Thursday expressed concern with the “alarming trend” in the uptick of the city’s daily coronavirus positivity rate.

The uptick is “reminiscent of the rise that we saw last October,” Lightfoot said during a conference call with reporters this afternoon. The city’s positivity rate has jumped from 2.9% to 3.4%, with new COVID-19 cases averaging 365 a day. That number was around 100 a week ago. Under the city health department metrics, that increase puts the city in the “High Risk” category.

The increase in cases is being driven by 18- to 39-year-olds and is concentrated on the North and Northwest sides of Chicago, including the neighborhoods of Lincoln Park, Dunning, Old Town and Portage Park.

It’s the same cohort of Chicagoans the city has had problems with controlling throughout the pandemic, the mayor said, adding: “We were all young once. We all think we’re invincible. We never think that something bad is going to happen to us.”

“So we are doing a significant amount of outreach and messaging to reach these young people,” Lightfoot said. “But the bottom line is we’re seeing a very disturbing trend that could significantly impact our ability to move forward with reopening.”

As the mayor raised the alarm about the growing positivity rate, her public health and business affairs departments announced it will be allowing expanded outdoor capacity for bars, restaurants and other events, like weddings or outdoor fitness classes.

For bars and restaurants, tables outdoors can sit up to 10 people. Overall capacity is increasing to 100 individuals or 50% capacity, whichever is less.

Large outdoor venues, those that can accommodate more than 200 people, can operate at 25% capacity. Smaller venues that could normally hold 50 people or less can operate at 50%. Outdoor places of worship are exempt from limits as long as people keep six feet apart, while outdoor fitness classes are capped at 100 people.

To keep indoor limits uniform among industries, the city is allowing an increase to indoor fitness classes to 50% or up to 50 people.

Lightfoot said she doesn’t think she’s sending mixed signals by increasing outdoor capacity while raising the alarm about the positivity rate.

“The issue that we face really isn’t around outdoor events,” Lightfoot told reporters on the conference call. “And we’re still being prudent there. The issue that we’re seeing is people not following the public health guidance around masking social distancing, particularly indoor activities.”

The mayor has gone on the record stressing that she is not interested in “shutting everything down.” She repeated that sentiment on Thursday, saying she prefers a more targeted approach than going into another lockdown as is the case in Europe right now.

This latest rise in positivity shouldn’t have an impact on the city’s plan to reopen high schools, the mayor said, adding that the city and school district have put a “tremendous” amount of money and resources to keep schools safe.

Chicago Public Schools has a target date to reopen high schools for in-person learning on April 19. But it is still negotiating the date and the terms of the reopening with the Chicago Teachers Union.

Claudia Morell covers city politics for WBEZ. Follow @claudiamorell.