About Measles: Symptoms, Complications, Who Is at Risk and Prevention

Some people think of measles as a little rash and fever that clear up in a few days. It is not. Measles can cause serious complications, especially in children younger than 5, and it is highly contagious: if one person has it, up to 9 out of 10 people who come into close contact with them will become infected if they are not protected. Anyone without protection is at risk. Two doses of the measles, mumps and rubella (MMR) vaccine give the best protection, and it lasts a long time.

Signs and symptoms

Symptoms appear 7 to 14 days after contact with the virus. The common ones are:

• high fever, which may spike above 104 °F;
• cough;
• runny nose (coryza);
• red, watery eyes (conjunctivitis, or pink eye);
• rash.

Complications

Complications are most likely in children younger than 5. The common ones are ear infections and diarrhea. The serious ones are pneumonia, encephalitis (swelling of the brain) and, in some cases, death.

Measles can cause serious complications at any age, but some groups are at higher risk of severe ones:

• children younger than 5;
• adults older than 20;
• pregnant women;
• people with weakened immune systems, for example from leukemia or HIV infection.

Who is at risk

Measles was declared eliminated from the United States in 2000. But since early 2025, U.S. cases have been rising, with several large outbreaks of more than 50 cases. Measles is still common in many parts of the world, and every year unvaccinated travellers — mostly Americans, sometimes visitors from abroad — catch it in other countries and bring it back to the United States.

How it spreads

Measles spreads through the air when an infected person coughs or sneezes. You can catch it simply by being in a room where someone with measles has been — even up to 2 hours after they have left.

Prevention

The MMR vaccine is the best protection. It is safe and effective, and serious reactions are extremely rare. Two doses are about 97% effective at preventing measles; one dose is about 93% effective. Talk with a health care provider about the MMR vaccine, especially before travelling.

Health care providers can find CDC's guidance on what to do when a patient may have measles or has been exposed in its clinical overview and its alert on staying watchful for measles cases.

Sources

• Centers for Disease Control and Prevention, "About Measles": https://www.cdc.gov/measles/about/index.html
• Rewritten in hubnx's own words.
• The page's illustration of the virus is not reproduced.