Measles virus, genus Morbillivirus and family Paramyxoviridae.
Transmission, which is primarily by airborne respiratory droplets, increases during the late winter and early spring in temperate climates and after the rainy season in tropical climates.
Nature of the disease
Measles is a highly contagious infection; before vaccines became available, this disease had affected most people by the time of adolescence. Epidemics may still occur every 2 or 3 years in areas where there is low vaccination coverage. In countries where measles has been largely eliminated, cases imported from other countries remain an important continuing source of infection. In 2009, worldwide measles vaccination coverage had reached 82%, and between 2000 and 2008 the estimated annual number of deaths from measles dropped from 733 000 to 164 000.
The classical signs and symptoms of measles include fevers, cough, nasal congestion, and rashes. Common complications include bacterial middle-ear infection and pneumonia. In addition to infants, high-risk groups for measles complications include individuals suffering from chronic diseases and impaired immunity or from severe malnutrition (including vitamin A deficiency).
Before vaccines became available, measles outbreaks occurred all over the world. Since the introduction of large-scale measles immunization, indigenous transmission has virtually stopped in the Americas and in many industrialized countries worldwide.
Risk for travellers
Measles is still common in many countries and travel in densely populated areas may favour transmission. Travellers who are not fully immunized against measles are at risk. Special attention must be paid to all children and adolescent/young adult travellers who have not received two doses of measles vaccine.