Measles is a highly contagious disease that is caused by a virus.
Measles is spread when an infected person coughs or sneezes. Small droplets containing the virus disperse into the air and onto nearby surfaces, where the virus can live for up to 2 hours. Another person can become infected by breathing contaminated air or through contact with a contaminated surface. A person who is infected with measles can spread the disease to others even before any symptoms appear.
Measles is one of the most contagious diseases known. This means that it spreads easily from an infected person to others who are not immune to the disease. People who are fully vaccinated against measles, who have had the disease, or who were born in the United States before 1957 are considered immune.
Early symptoms appear 1 to 2 weeks after a person is exposed to the disease. Symptoms include fever, cough, runny nose, and red, watery eyes. Red spots, sometimes with small bumps, appear on the skin 3 to 5 days later. The rash starts on the head and spreads downward to other parts of the body. A high fever may occur when the rash appears. Symptoms resolve a few days later.
Complications from measles are more likely in children younger than 5 years or adults older than 20 years. Ear infections and diarrhea are common. Serious complications occur less often. They include pneumonia (lung infection) and encephalitis (swelling of the brain). Severe complications can lead to permanent brain damage or death. In pregnant women, measles infection may lead to premature labor or a low-birth-weight baby.
Vaccination against measles began in the United States in 1963. Before that time, measles infected an estimated 3 million to 4 million people in the United States each year and caused about 48 000 hospitalizations and 500 deaths. The measles vaccine program has been so effective that between 2001 and 2010 there were fewer than 150 cases per year in the United States.
Even though the chance of being infected with measles in the United States is low, being vaccinated is still important. Unvaccinated people who live in or travel to countries where measles is still common can bring the disease into the United States. Outbreaks can then occur in areas where vaccination rates are low.
In recent years, measles cases in the United States have almost always affected people who were not vaccinated or whose vaccination status was unknown. Since 2012, the number of reported measles cases has increased dramatically. In 2014, there were 644 cases in 27 states. In the first 5 weeks of 2015 alone, there were 121 cases affecting people in 17 states.
Centers for Disease Control and Preventionwww.cdc.gov/measles/index.html
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Sources: Centers for Disease Control and Prevention, World Health Organization
Topic: Infectious Disease
Thompson AE. Recognizing Measles. JAMA. 2015;313(15):1584. doi:10.1001/jama.2015.1889