The epidemiology of measles

Abstract

Measles is a highly infectious disease which has a major impact on child survival, particularly in developing countries. The importance of understanding the epidemiology of this disease is underlined by its ability to change rapidly in the face of increasing immunization coverage. Much is still to be learned about its epidemiology and the best strategies for administering measles vaccines. However, it is clear that tremendous progress can be made in preventing death and disease from measles with existing knowledge about the disease, and by using the presently available vaccines and applying well-tried methods of treating cases. Research in the coming decade may provide more effective vaccines for use in immunization programmes. An understanding of the basic epidemiology of measles is a prerequisite for effective control measures.

PIP: The Expanded Programme on Immunization (EPI) dramatically increased coverage. In 1990, approximately 80% of the world's children younger than 1 year received measles vaccine, and it was estimated that around 2 million deaths were prevented. Still in 1990 an estimated 45 million cases and around 1 million deaths occurred in developing countries. In one community study in Kenya in 1985 measles accounted for 35% of reported deaths in infants 1-12 months old and for 40% of deaths in children 1-4 years old. The Schwarz vaccine was introduced in the 1960s; under most field conditions its efficacy is about 85% for children receiving the vaccine at 9 months or older. The urban poor, who usually have less access to immunization services, are usually the most at risk. Other high-risk groups include specific age groups (school children who represent cohorts from previous years when coverage was lower and who may not have been exposed to measles infection), ethnic minorities (who may have been underserved or may have rejected immunization for cultural reasons), hospitalized children who are at high risk of nosocomial transmission, and children in refugee camps. Vitamin A administered to children acutely ill with measles reduces mortality. Results from a trial in South Africa showed children treated with vitamin A had reduced risk of dying, recovered more quickly from pneumonia and diarrhea, and had less croup. In addition, symptomatic treatment for cases requires antibiotics to combat bacterial complications, and oral rehydration salts for dehydration following diarrhea. Case fatality rates can be lowered if cases reach health care facilities where appropriate care is offered early. For uncomplicated cases, supportive fluids, antipyretics, and nutritional therapy may be required. Many children need increased food intake for 4-8 weeks to recover their premeasles nutritional status.