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Measles

The first measles cases this year in suburban Cook County and Chicago were announced on April 30, 2025. Learn more in this press release.

Myth or Fact

Test your measles knowledge before and/or after reading this page. Take the Measles Myth or Fact Quiz.

About Measles

Measles is a serious respiratory disease (in the lungs and breathing tubes). It causes a rash and fever. It is very contagious. In rare cases, it can be deadly.

How Measles Is Spread

Measles is so contagious that 90 percent of unvaccinated people will get it, if exposed. Measles is easily spread through the air when someone coughs or sneezes. People can also get sick when they come into contact with mucus or saliva from an infected person.

Measles Symptoms

Early symptoms (first few days):

  • Moderate fever
  • Cough
  • Runny nose
  • Red eyes
  • Sore throat

Later symptoms (after a few days):

  • Blue-white spots inside the mouth (Koplik spots)
  • Red-brown rash that starts at the hairline and spreads down the body
  • High fever (can go over 104°F)

The rash usually appears 14 days after exposure. Some immunocompromised people may not develop the rash.

How Long is a Person Contagious?

People are contagious about four days before their rash starts to four days after it appears. If you might have measles, stay home during this time.

Complications From Measles

Complications from measles can lead to pneumonia, seizures, hearing loss, life-long brain damage and death.

Best Protection From Measles

The CDC recommends two doses of the MMR vaccine for lifelong protection. If unsure, you can check your vaccine history. MMR is safe and effective. Two doses of MMR vaccine are about 97% effective at preventing measles; one dose is about 93% effective.

Prevent measles and talk to your healthcare provider about the MMR vaccine, especially if planning to travel.

Immunization records recorded in the Illinois immunization registry can be accessed using the Illinois Department of Public Health Vax Verify portal .

Unvaccinated individuals who do not have a healthcare provider are encouraged to contact Cook County Health at 312-864-1111 to schedule a vaccination appointment at a community health center in Chicago or suburban Cook County.

Measles and International Travel

Measles Prevention During International Travel:

Measles cases in the United States originate from unvaccinated international travelers. Here are tips to help prevent measles during international traveling:

  • You should be fully vaccinated against measles at least two weeks before international travel.
  • Two doses of MMR vaccine provide 97% protection against measles.
  • If your trip is less than two weeks away and you’re not protected, you should still get a dose of MMR.
  • Infants under 12 months old who are traveling should get an early dose of the MMR vaccine at 6 through 11 months. They should get another dose at 12 through 15 months and a final dose at 4 through 6 years.

After Returning From International Travel:

  • Watch your health for three weeks after you return. Measles is highly contagious and can spread to others through coughing and sneezing.
  • Measles symptoms typically include:
    • High fever (may spike to more than 104° F)
    • Cough
    • Runny nose (coryza)
    • Red, watery eyes (conjunctivitis or pink eye)
    • Rash (3-5 days after symptoms begin)
  • Call your doctor immediately if you think you or your child have been exposed to measles.

Visit the CDC website to learn more .

Additional Resources

For Healthcare Facilities: Measles Preparation and Mitigation Guidance

Communications Resources

Updated May 16, 2025, 2:49 PM