Chicago's travel order was updated once again Tuesday, with Puerto Rico now on the city's quarantine list.
Last week, the city added four new states to its order - Wisconsin, Missouri, North Dakota and Nebraska - bringing the total number of states the city requires travelers to quarantine from to 22.
The city's travel order is evaluated every Tuesday, with any additions taking effect the following Friday.
States are added to the list if they have "a case rate greater than 15 new COVID-19 cases per 100,000 resident population, per day, over a 7-day rolling average." If they fall below that threshold, they could be removed as well.
On Tuesday, the city's top public health official said three states - Iowa, Kansas and Utah - dropped below the threshold to be on the travel order, and could be removed next week if those numbers continue to decline.
Chicago's travel order first began on July 6.
The states included are: Alabama, Arkansas, Arizona, California, Florida, Georgia, Idaho, Iowa, Kansas, Louisiana, Mississippi, Missouri, Nebraska, Nevada, North Carolina, North Dakota, Oklahoma, South Carolina, Tennessee, Texas, Utah and Wisconsin.
"We're watching all of our neighbors very, very carefully and we're going to be very prudent," Chicago Mayor Lori Lightfoot said last week.
So far, Indiana has not been added to the city's list.
"Indiana doesn't quite rise to that level, which is a good thing for the residents of the Hoosier state but we're watching all of our neighbors very carefully," Lightfoot said.
Chicago Department of Public Health Commissioner Dr. Allison Arwady said travelers entering or returning to Chicago from "states experiencing a surge in new COVID-19 cases" will need to quarantine "for a 14-day period from the time of last contact within the identified state." Essential workers could be exempt from the quarantine requirement, however, as long as their employer certifies their work in writing.
The order is set to remain in effect until further notice.
The move comes as states across the U.S. see surges of coronavirus cases, many shutting down bars and restaurants in an effort to quell or prevent a spike.
New cases have surged in several states across the nation, setting new records, driven mostly by expanding outbreaks in the American South and West.
New York and New Jersey are also asking visitors from several states from the Carolinas to California to quarantine themselves for two weeks.
Still, outside of Chicago, Illinois Gov. J.B. Pritzker said the state likely won't require residents who travel to and from neighboring states to quarantine for two weeks solely because of that travel.
"We don't live in a country where you close the borders between states," Pritzker said during the governor's coronavirus briefing. "And we're not going to stop people who live in Illinois and work in Wisconsin from doing so."