measles or rubeola ro͞obēˈələ [key], highly contagious disease typically contracted during childhood, caused by a filterable virus and spread by droplet spray from the nose, mouth, and throat of individuals in the infective stage. This period begins 2 to 4 days before the appearance of the rash and lasts from 2 to 5 days thereafter. The first symptoms of measles, after an incubation period of 7 to 14 days, are fever, nasal discharge, and redness of the eyes. Characteristic white spots appear in the mouth, followed by a rash on the face that spreads to the rest of the body. The symptoms disappear in 4 to 7 days.

One attack of measles confers lifelong immunity. However, it renders the patient susceptible to other more serious infections such as bronchial pneumonia and encephalitis; it also infects immune cells, and disrupts the immune system's ability to resist diseases to which the body has previously been exposed. The measles virus has also been associated with subacute sclerosing panencephalitis (SSPE), which causes chronic brain disease in children and adolescents. After the attack of measles, it can cause intellectual deterioration, convulsive seizures, and motor abnormalities and is usually fatal. Common measles in pregnant women can be a threat to the unborn child, and vaccination of women well before pregnancy is recommended (see also rubella, or German measles).

Immunization by injection of live measles-virus vaccine, first marketed in 1963, has proved effective. Given at first with gamma globulin, the vaccine was further developed by 1965 so that one shot alone gives long-term, probably lifetime, immunity; a nationwide program was established in the United States for the vaccination of all children over the age of nine months. Measles has been eliminated in the Americas, but epidemics still occur in regions where vaccination rates are low and health care is poor, and outbreaks can occur in the Americas when infected persons travel there from other regions. Worldwide, measles declined until 2017, when cases began to rise in part because of the expense or difficulty of vaccination in some developing countries; lack of vaccination in some groups in developed countries, for a variety of reasons, has also increased the number of cases in outbreaks caused by travelers transmitting the virus.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.

See more Encyclopedia articles on: Pathology