Measles is a disease reported throughout the world.
Epidemics of measles occur every 2–3 years. Approximately, 30 million cases of measles are reported annually, most cases being from Africa. The condition has also been well docu-mented in the America, Europe, Eastern Mediterranean region, Western Pacific region, and Southeast Asia.
Measles is exclusively a human disease. Infected respiratory droplets are the primary source of infection. Patients are infec-tious from 3 days before the onset of illness until the rash desquamates. Infectivity is maximum at the prodrome and diminishes rapidly with the onset of the rash. The infection is transmitted from person to person by inhalation of large drop-let aerosols produced during the act of coughing and sneezing.
Children with immunodeficiency due to leukemia, cortico-steroid therapy, or HIV are at increased risk for infection regard-less of their status of immunization. Unvaccinated people are also at risk. The condition is most commonly seen in children living in crowded condition.