Measles, also rubeola, acute, highly contagious, fever-producing disease caused by a filterable virus, different from the virus that causes the less serious disease German measles, or rubella. Measles is characterized by small red dots appearing on the surface of the skin, irritation of the eyes (especially on exposure to light), coughing, and a runny nose. About 12 days after first exposure, the fever, sneezing, and runny nose appear. Coughing and swelling of the neck glands often follow. Four days later, red spots appear on the face or neck and then on the trunk and limbs. In 2 or 3 days the rash subsides and the fever falls; some peeling of the involved skin areas may take place. Infection of the middle ear may also occur.
Measles was formerly one of the most common childhood diseases. Since the development of an effective vaccine in 1963, it has become much less frequent. By 1988, annual measles cases in the U.S. had been reduced to fewer than 3500, compared with about 500,000 per year in the early 1960s. However, the number of new cases jumped to more than 18,000 in 1989 and to nearly 28,000 in 1990. Most of these cases occurred among inner-city preschool children and recent immigrants, but adolescents and young adults, who may have lost immunity from their childhood vaccinations, also experienced an increase. In 1991, the number of new cases dropped to fewer than 10,000. The reasons for this resurgence and subsequent decline are not clearly understood. In other parts of the world measles is still a common childhood disease. In the U.S., measles is rarely fatal; should the virus spread to the brain, however, it can cause death or brain damage.
No specific treatment for measles exists. Patients are kept isolated from other susceptible individuals, usually resting in bed, and are treated with aspirin, cough syrup, and skin lotions to lessen fever, coughing, and itching. The disease usually confers immunity after one attack, and an immune pregnant woman passes the antibody in the globulin fraction of the blood serum, through the placenta, to her fetus.
Most viral infections cause no symptoms and do not result in disease. For example, only a small percentage of individuals who become infected with Epstein-Barr virus or western equine encephalomyelitis virus ever develop disease symptoms. In contrast, most people who are infected with measles, rabies, or influenza viruses develop the disease. A wide variety of viral and host factors determine the outcome of virus infections. A small genetic variation can produce a virus with increased capacity to cause disease. Such a virus is said to have increased virulence.