5 additional measles cases bring Chicago's outbreak total to 31

Five more measles cases were reported by Chicago health officials on Tuesday.

The city has reported 31 measles cases since an outbreak in early March. Those were the first cases of the disease detected in Chicago since 2019.

Children ages 4 and younger account for 21 of the city’s total cases, according to the Chicago Department of Public Health.

Many of the measles cases have been reported at a migrant shelter in Pilsen, where residents were urged to receive a second dose of the measles vaccine 28 days after the first shot, health officials said Monday.

The 31 measles cases in Chicago make up almost all of the cases this year in Illinois. Lake and Will counties each have reported one case, according to the Illinois Department of Public Health.

Illinois hasn’t had this many measles cases in a year in at least 15 years, according to the IDPH. The most recent year with double-digit cases was 2015, when 17 measles cases were reported in the state.

Cases of the disease have soared this year, with the CDC reporting 64 measles cases in the U.S. as of March 21. The agency reported 58 cases in all of 2023.

Symptoms, including high fever, cough, runny nose, and red or water eyes, can emerge within a week or two of exposure to the virus, according to the U.S. Centers for Disease Control and Prevention. A rash can appear three to five days after initial symptoms begin.

The "highly infectious" virus is spread through coughing, sneezing or contact with an infected person, and the virus can live for up to two hours in the air after an infected person has left a space, according to the CDC. Those with the virus can spread it up to four days before and after a rash appears, and 90% of people without immunity who are exposed to the virus become infected.

Health officials say vaccination is the key way to avoid getting measles and spreading it.

A CDC team has been assisting the city in responding to the infections.