Nearly every measles infection results in well-recognized clinical disease. In nonimmunized populations almost every child will get measles early in life. The universality of the disease in nonimmunized communities, particularly those in the developing world, has led to a more or less passive acceptance of measles as an unavoidable risk of early life. The clinical spectrum of measles ranges from a mild, self-limiting illness to a fatal disease. Conditions encountered mainly in the developing world, e.g., unfavorable nutrition, high risk of concurrent infection, and inadequate case management -- particularly at home -- favor the development of complications and adverse outcome. Conversely, good clinical management of an otherwise healthy child, a situation seen mostly in the developed world, greatly influences the course of the disease. Hence many in the medical profession believe that measles is a mild disease except among populations living under particularly unfavorable conditions. Measles vaccine is effective in preventing disease in the individual and in controlling it in the community if it is given at the critical age when maternal antibodies wane and the risk of natural infection increases sharply and if a high immunization rate is maintained in the target population. The experience with immunization, particularly in sub-saharan Africa, is rewarding: mothers who had previously accepted measles as an unavoidable risk clamour for immunization of their children once its effectiveness has been demonstrated. No reason exists for measles to claim its present toll of morbidity and mortality. With extension of the Expanded Programme on Immunization of the World Health Organization, the impact of measles should progressively decline.
PIP: This summary of the worldwide impact of measles discusses epidemiology, reported incidence, clinical severity, community attitudes toward measles, and the impact of immunization programs on measles. Measles, 1 of the most ubiquitous and persistent of human viruses, occurs regularly everywhere in the world except in very remote and isolated areas. Strains of measles virus from different counties are indistinguishable, and serum antibodies from diverse population have identical specificity. Yet, the epidemic pattern, average age at infection, and mortality vary considerably from 1 area to another and provide a contrasting picture between the developing and the developed countries. In the populous areas of the world, measles causes epidemics every 2-5 years, but in the rapidly expanding urban conglomerations in the developing world, the continuous immigration from the rural population provides a constant influx of susceptible individuals and, in turn, a sustained occurrence of measles and unclear epidemic curves. In the economically advanced nations, measles epidemics are closely tied to the school year, building up to a peak in the late spring and ceasing abruptly after the summer recess begins. Maternal antibody usually confers protection against measles to infants during the 1st few months of life. The total number of cases of measles reported to WHO for 1980 is 2.9 million. Considering that in the developing world alone almost 100 million infants are born yearly, that less than 20% of them are immunized against measles, and that various studies indicate that almost all nonimmunized children get measles, less than 3 million cases of measles in 1980 is a gross underestimate. There was adecrease in the global number of reported cases of measles during the 1979-80 period due primarily to the reduction in the number of cases in the African continent and, to a lesser extent, in Europe. It is premature to conclude that such a reported decline is real and that it reflects the beginning of a longterm trend. The contrast between the developed and the developing worlds is most marked in relation to the severity and outcome of measles. Case fatality rates of more than 20% have been reported from West Africa. It has been estimated that 900,000 deaths occur yearly in the developing world because of measles, but data available to WHO indicate that the global case fatality rate in the developing world approaches 2% (in contrast to 2/10,000 cases in the US), and the actal mortality may be greater than 1.5 million deaths per year. The advent of WHO's Expanded Program on Immunization has brought about an awareness of the measles problem. Whenever and wherever measles vaccine has been used effectively on a large scale, a marked reduction in the number of cases has been recorded.