Mode of transmission: Droplet (aerosol) infection.
Incubation period: 1 to 2 weeks.
The pre-eruptive stage: the virus is in the blood causing fever, rhinorrhea and cough. Koplik's spots appear in buccal mucosa (almost pathognomonic). These consist of small 2mm white spots (like grains of salt) surrounded by a reddish (erythematous) area on the mucous membranes opposite the 2nd molars. The pre-eruptive stage is also the infectious stage.
The eruptive stage: The characteristic centrifugal rash appears behind the ears and on the forehead, it then spreads to the rest of the face, and the trunk. In about a day or two it spreads to the limbs. Lesions coalesce and then become less similar (than say German measles). As it heals it may leave areas of desquamation.
An attack of measles confers a high degree of immunity and second attacks are uncommon.
Diagnosis is usually evident from the clinical picture. Investigations are seldom needed and consist of antibody detection by ELISA and culture of nasopharyngeal specimens during the pre-eruptive stages.
Usually only treatment of the symptoms is required. Antibiotics are given in the case of secondary bacterial infection. In infants and immunocompromised individuals passive immunization are given within six days after exposure.
Active immunization involves a single dose of live attenuated measles and is usually combined with the vaccines for mumps and rubella (MMR) in children.