Measles appears in Chicago for the first time in five years

A team of Centers for Disease Control and Prevention (CDC) experts is set to make its way to Chicago to help public health officials manage the city’s first known measles cases since 2019.

The Chicago Department of Public Health (CDPH) announced its first measles case last Thursday, and has since identified an additional cluster of four unrelated cases—some stemming from the city’s migrant shelter.

“[W]e are strongly urging those who aren’t vaccinated to do so as soon as possible, new arrivals and all Chicagoans. It is by far the best protection against measles, which for the first time in years is in our city,” CDPH Commissioner Olusimbo “Simbo” Ige said in a statement on Sunday. “Because of how contagious measles is, I anticipate seeing more cases.”

Measles is a highly contagious respiratory infection that can cause a host of complications, including pneumonia. According to the CDC, about 20% of infections among unvaccinated US residents lead to hospitalizations. However, the measles-mumps-rubella (MMR) vaccine offers effective protections against the disease. A single dose of the MMR vaccine offers 93% protection from measles, and a booster raises that figure to 97%, according to the CDC.

The cases come as vaccination rates among children have declined across the US to 93.1% from 2022–23, down from 95.2% during the 2019–20 school year, per CDC figures.

According to the CDPH, the first patient is recovering at home.

The four additional patients, including two children, all stayed in the same migrant shelter. One child has since recovered and the other is in stable condition; the two adult patients are also in stable condition, CNN reported.

The addition of CDC experts will help the CDPH to expand screenings of Chicagoans and distribute the vaccine, according to CNN.

The shelter outbreak spurred city health officials to screen shelter residents. CNN also reported that about 700 residents had existing immunity to measles, and city health officials vaccinated more than 900 additional residents at the shelter who lacked protection.

In a statement, Ige encouraged “the unvaccinated to get the vaccine and to immediately quarantine if you have had contact with anyone with measles.”

The US eliminated measles in 2000, though the disease has intermittently reappeared, most prominently in 2019 when the country saw 1,274 cases. This year, the CDC has documented 45 cases of measles in the US, compared to 58 in 2023.

The CDC noted that measles outbreaks can occur in “communities with pockets of unvaccinated people.”