(CHICAGO) — Chicago health officials have confirmed the city’s first measles cases since 2019 amid a rising number of infections across the U.S.

The first case was confirmed Thursday in a city resident whose source of infection is unknown, according to the Chicago Department of Public Health (CDPH), as reported by local ABC News affiliate ABC 7 Chicago.

The infectious period ended Wednesday and the patient is currently recovering well at home, health officials said.

On Friday, a second case was confirmed in a young child staying at a new arrivals shelter in the Pilsen neighborhood, in the city’s Lower West Side, health officials said in a release provided to ABC News. Similar to the first patient, the child has since recovered and is no longer infectious, according to officials.

No identifying information was provided about either patient, including names, ages, sex or race/ethnicity.

Health officials said people may have been exposed to the first patient on Feb. 27 either at Galter Medical Pavilion at Swedish Hospital between 8:30 a.m. CT and 12 p.m. CT, or on Chicago Transit Authority Bus 92 (Foster) between 9:15 a.m. CT and 11:30 a.m. CT, ABC 7 Chicago reported.

For the child shelter resident case, it’s unclear who may have been exposed so the CDPH is asking all residents of that shelter, located in the 2200 block of S. Halsted St., to remain in place so health officials can determine if the residents have been previously vaccinated against measles.

“Those who have been vaccinated can go about their normal business while those who have not been vaccinated will have to remain indoors to watch for symptoms,” the CDPH said. “All unvaccinated residents will be screened for symptoms and offered the measles vaccine.”

The CDPH further said it is delivering masks and other personal protective equipment for shelter residents and staff, and that the Department of Family and Support Services has secured additional meals for those staying on site.

Health officials added that most Chicago residents are routinely vaccinated with the measles, mumps and rubella (MMR) vaccine in childhood and so are not at high risk for contracting measles.

Last month, the CDPH said it was investigating a possible measles exposure in Chicago, after a northwest Indiana resident with a confirmed case of measles sought medical care at three Chicago hospitals while contagious between Feb. 11 and Feb.16. It’s unknown if the two confirmed Chicago cases are linked to the Indiana case.

“The MMR vaccine is 97% effective at stopping transmission of measles and has enabled us to live in a time when seeing cases of measles at all is a rarity,” CDPH Commissioner Dr. Olusimbo Ige said in a statement at the time. “It is never too late to get vaccinated against this virus, not only to protect yourself but also to protect those around you who may be unable or too young to be vaccinated themselves.”

Measles was declared eliminated in the U.S. in 2000, but pockets of unvaccinated or under-vaccinated communities have led to sporadic outbreaks over the last several years.

As of Feb. 29 of this year, 41 measles cases have been reported in 16 states – California, Florida, Georgia, Indiana, Louisiana, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York, Ohio, Pennsylvania, Virginia and Washington – according to the Centers for Disease Control and Prevention. Illinois is now the 17th state to see measles cases.

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