CHICAGO — City public health officials Tuesday added Hawaii, Nebraska, and North Carolina to its travel quarantine order, and Indiana could be next.

Chicago Public Health Commissioner Dr. Allison Arwady said Indiana has reached the infection-rate threshold — more than 15 new daily COVID-19 cases per 100,000 residents over a week period — that requires Chicagoans that spend more than 24 hours in high-risk states to self-quarantine for 14 days.

City officials stopped short of adding Indiana to the list of 21 states and Puerto Rico this week citing lower infection rates last week, the state’s recent reporting antigen-positive tests that added about a thousand in a single day, and spikes in cases at college campuses including Notre Dame and Ball State universities.

But Arwady made it clear at a Tuesday news conference: “We have concerns about Indiana.”

“If we don’t see improvement across the state, we will then add them next Tuesday. So we’re keeping an eye on it, really hoping that that is more of a data reporting anomaly, but we have some real concern,” she said.

As of Tuesday, Alabama, Arkansas, California, Florida, Georgia, Hawaii, Idaho, Iowa, Kansas, Louisiana, Mississippi, Missouri, Nebraska, Nevada, North Carolina, North Dakota, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, and Puerto Rico are on the city’s travel quarantine list.

Arwady said there also continues to be a slow increase in coronavirus case in Chicago.

“We are not out of the woods,” Arwady said Tuesday. Hospitalizations and deaths from coronavirus remain stable. Chicago has about 348 positive tests per day, and a test-positivity rate of 5.3 percent over the last seven days, Arwady said.

“It is not the time to relax your guard,” she said. “It is not the time to be getting together unnecessarily.”