Measles is an illness caused by a virus. It is highly contagious; it travels through the air and can survive on surfaces for up to 2 hours. The symptoms of measles include a high fever, a sore throat, a runny nose, and red eyes. It also causes small white bumps in your mouth (called Koplik spots) and a red, bumpy rash that appears a few days after the other symptoms.
In the U.S., around one in four people who catch measles will need treatment in a hospital. It’s especially dangerous to children under the age of 5 and adults over 20. Complications can include severe ear infections (which may lead to hearing loss), bronchitis, pneumonia, and diarrhea. Rarer complications include encephalitis (a brain infection), problems during pregnancy, and subacute sclerosing panencephalitis, a fatal illness impacting the nervous system that occurs in some people 7 to 10 years after they have measles.
Measles is rare in the U.S. thanks to the measles-mumps-rubella (MMR) vaccine, which prevents measles in 97% of people after two doses. The MMR vaccine is safe for most people and does not cause autism. Some people, including pregnant women, people with some allergies, and people with weakened immune systems, should not get an MMR vaccine.
Normal side effects of the MMR vaccine can include: