How measles spreads and other facts

A Louisville pediatric infectious disease specialist answers common questions about measles, including steps parents can take to prevent infection.

Author: Norton Children's

Published: March 3, 2025

Estimated reading time: 6 minutes

Measles is spread easily among those who aren’t vaccinated and can have life-threatening complications, especially in young children. It also can leave those who had it vulnerable to infections for years after recovering, according to Kristina K. Bryant, M.D., a pediatric infectious diseases physician with Norton Children’s Infectious Diseases.

Thanks to widespread adoption of the MMR (measles, mumps and rubella) vaccine, the disease had been considered eliminated in 2000. But falling immunization rates have allowed the measles virus to become a threat again.

Dr. Bryant offers some facts about preventing, diagnosing and treating a measles infection.

What is measles?

Measles is a serious viral illness that can have long-term health consequences. The good news is that it can be prevented with vaccines that are very effective. The best way to protect your child and to protect your family is to make sure that everybody is up to date with their recommended vaccines.

Why is measles in children a concern?

Children, especially those younger than 5, are more likely to develop severe or complicated infections. The virus can lead to pneumonia and rarely other life-altering condition like brain damage and deafness. According to the Centers for Disease Control and Prevention (CDC), nearly a third of children younger than age 5 who have measles have to be hospitalized.  About 1 to 3 of every 1,000 children who become infected with measles will die.

How is measles spread?

It’s very contagious. You can catch measles just by being in a room where a person with measles has been, up to two hours after that person is gone. Nine out of 10 susceptible people in a room will get infected if exposed to the virus.

The virus spreads through the air. When a person who is infected with the measles virus talks or coughs or sings, that virus goes into the air — and other people breathe it in. And if they don’t have immunity against measles, they can get sick. 

Unlike with some other viruses, infectious measles droplets can hang in the air for up to two hours after the infected person leaves the room.

What are measles symptoms?

Measles symptoms include fever, cough, congestion, runny nose and red, watery eyes. Several days after the start of symptoms, a rash occurs. It usually starts on the head and spreads down the body.

Measles rash spots typically are flat, but may develop into small bumps. As the spots spread, they may join together. A high fever is possible (more than 104°), and some children will have diarrhea. Young children, particularly those under age 5, are at risk for severe measles and measles complications.

What are the potential complications of measles?

Common complications include ear infection, pneumonia and other bacterial infections. Children can develop diarrhea with dehydration. 

Rarely, kids can develop severe complications, including encephalitis, a life-threatening inflammation of the brain. That occurs in about 1 in 1,000 cases. Even after a patient recovers, measles can suppress the immune system and make the person susceptible to viral and bacterial infections for several years.

What are measles risk factors?

People who haven’t been vaccinated are at risk. This includes babies younger than 12 months, because they are too young to receive the vaccine. Pregnant women, kids younger than 5, adults older than 20, and people with a weakened immune system are at highest risk for complications from measles.

Who should get vaccinated?

The MMR vaccine is recommended for kids at 12 to 15 months old. They’ll need another dose when they start school at age 4 to 6. For families traveling internationally, the MMR vaccine is recommended for infants as young as 6 months. They’ll get the early dose, then the two recommended doses at the usual age.

In the case of a child who received one dose of measles vaccine, but didn’t get the second, it can be administered without having to restart the series.

The CDC considers people to be protected for life if they received two doses of measles vaccine according to the appropriate schedule.

About 3% of people who get two doses of measles vaccine still will get measles if exposed. However, fully vaccinated people are likely to have a milder illness. They’re also less likely to spread the disease to other people, including those who can’t get vaccinated.

Do I need a booster dose of vaccine?

No. People who received two doses of measles vaccine as children according to the U.S. vaccination schedule are considered protected for life and they do not ever need a booster dose. Unvaccinated adults or those who received a version of the vaccine before 1968 should consult their primary care provider.

Is there a measles treatment?

There’s no specific treatment, which is why prevention (vaccination) is so important. Medications often are used to treat some of the symptoms of measles, but the virus itself has to run its course.

If I’m pregnant, should I be concerned about my baby?

Most women of childbearing age have been vaccinated and therefore are protected. If a nonimmune pregnant woman is exposed to measles, it may cause health issues both for her and her unborn baby. In a CDC study, the most common effect to the mothers was pneumonia, and the most common effect on the baby was premature delivery. If mom is exposed within 10 days of delivery, it can cause a serious infection in her newborn at birth.

If a pregnant woman was not previously vaccinated against measles, she cannot receive the vaccine until after delivery.

My child might have been exposed to measles. What should I do?

If you think your child has been exposed to measles, tell your doctor. Children exposed to measles who have not yet received recommended vaccines may be able to receive a vaccine dose or a medication called immunoglobulin to help prevent infection. The health department is often involved in helping to determine if one of these treatments is needed and how long a person needs to stay home to avoid exposing others.

Watch for signs of sickness.If your child starts showing signs of having a cold or the flu, immediately call your pediatrician. It’s incredibly important to call first rather than walk in. This will give the office time to prepare to help protect others from exposure.

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