Outbreaks of measles—caused by a wildly contagious virus that was under control in the United States—are becoming more frequent. Getting the measles is especially risky for children too young for the vaccine or those with certain health conditions. Even in previously healthy children, measles can cause serious illness that lands them in the hospital. Learn why measles outbreaks are on the rise, the symptoms of measles, how the disease spreads and when to keep your child home from school.

Measles is a highly contagious disease caused by the measles virus. The infection can lead to serious and sometimes fatal complications. Fortunately, measles is a vaccine-preventable illness.

Measles was under control in the United States, but we are seeing outbreaks again in areas where vaccination rates have fallen.

The childhood and adolescent immunization program in the United States led to a more than 99% decrease in measles cases since 1963. However, travelers visiting or returning to the United States from other countries can spread measles to people who are at risk and cause an outbreak.

After the first measles infection is reported in a community, it is considered an outbreak because of how quickly measles spreads. Local health experts must work quickly to identify others who were exposed so they can stop measles from spreading to others.

How contagious is measles?

Measles is one of the most contagious diseases in the world. In fact, 9 out of 10 people exposed to measles will catch it, too, if they are unvaccinated, have not had the disease before or have a problem with their immune system. Even very brief exposure to an infected person in a shared space poses a high risk for unimmunized people.

How long is someone with measles contagious?

People with measles are contagious before they know they are sick. An infected person can spread measles easily to others 4 days before the rash appears, and they are still contagious 4 days after the rash appears.

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