Health officials have reported the first measles case in Illinois as part of the latest nationwide outbreak. The Illinois Department of Public Health said the case involves an adult in Southern Illinois and was confirmed through laboratory testing on April 23.

Here's what we know.

How is measles transmitted?

Measles is a serious, highly contagious disease caused by a virus, according to the IDPH. The disease can be spread by direct contact with an infected person's nose or throat secretions or through the air when an infected person sneezes or coughs.

How many measles cases in Illinois?

So far, the health department has only reported one case in Illinois in 2025. The department said in a press release, "The risk of measles transmission for the general public in Illinois remains low."

How many measles cases in the US?

The Centers for Disease Control and Prevention received reports of 800 confirmed measles cases nationwide in 2025 as of April 17. 96% of the cases involved individuals who were either unvaccinated against the measles virus or with an unknown vaccination status.

Of the 800 confirmed cases, 85 have resulted in hospitalizations. There have been two confirmed deaths caused by the virus, with an additional case under investigation.

Symptoms of measles

Fevers typically begin about 10 days after exposure, while rashes appear about 14 days after exposure.

How to protect against measles

The IDPH says vaccination is the best way to prevent measles. The MMR vaccine, which protects against measles, mumps and rubella, is recommended for children 12-15 months old, with a second dose recommended at 4-6 years old.

Most adults are recommended to receive at least one dose of the vaccine, excluding women who are pregnant or plan to be pregnant within the next three months.

The CDC says two doses of the vaccine are 97% effective against measles.

How to treat measles?

The IDPH says those with measles should stay home from work, school and other social activities while contagious. This period lasts from four days before the onset date of the rash through the end of the fourth day after the onset.

Those seeking medical attention should notify their local health facility ahead of time to arrange minimal exposure to others.

The disease cannot be treated with antibiotics or antiviral drugs, but the health department recommends bed rest, fluids and medicine for fevers and headaches.

Tracking measles cases

Illinois residents should check in regularly with the IDPH for any announcements about additional cases. The CDC is also tracking cases on its website , with data updated every Friday.

The IDPH has a Measles Outbreak Simulator Dashboard on its website that provides the measles vaccination rate in any public or private school in Illinois. The tool also allows residents to determine the risk of a child being exposed to measles if a case is introduced in their school.