DISEASES CHARACTERIZED BY CUTANEOUS LESIONS Measles is an extremely contagious, febrile disease of high morbidity characterized by rash and catarrhal inflammation of the eves and respiratory tract. in diameter. The virus is thermolabile, haring a half-life of two hours at 37° C.; it is also inactivated rapidly below pH 4.5. It has been found that tissue cultures derived from nonprimates, as well as from primates and chick embryos, will support propagation of the virus, as originally described by Enders and Peebles in 1954.
This reaction affords a method for titrating specific antibody in the serum. Prevalence and Epidemiology. It may occur at any time of the year, but most outbreaks are in the late winter and early spring, with a peak at the end of April. When the proportion of nonimmune reaches a certain crucial concentration (45 to 50 percent), disease and coincident dissemination of virus may occur to produce an epidemic. carrier state with unmodified measles to suggest local persistence of the virus in interepidemic periods.
DISEASES CHARACTERIZED BY CUTANEOUS LESIONS Beyond the age of ten more than 90 percent of the population have a specific antibody. Al-though the peak attack rate coincides with the beginning of school (age six) in technologically advanced societies, it occurs between the ages of two and three in most underdeveloped countries. Morbidity and mortality rates do not appear to be influenced by sex or race. Case fatality rates are highest in children less than five years of age and are also relatively high in the aged. The con-genital infection has occurred. A strikingly increased mortality rate is observed in areas such as West Africa in which protein-calorie malnutrition is prevalent.
Because measles virus per se rarely induces fatal disease, it is evident that fatalities attributable to measles may vary in incidence according to the prevalence of bacterial pathogens and the resistance of the population to their presence. Communicability. Demonstration of the virus in nasopharyngeal secretions is in accord with epidemiologic evidence that infection is disseminated and acquired by the respiratory tract. A detailed study of a family subject to recurrent attacks suggests a hereditary defect in the capacity to develop immunity in certain cases. One such patient was found to be capable of antibody formation, and electrophoretic analysis of the serum showed no deficit of gamma globulin.
Pathology and Physiologic Responses. Pneumonia is almost invariably present; it is most frequently interstitial, but may produce purulent exudate within the alveoli. More representative are changes of the uncomplicated viral disease within the tonsillar, nasopharyngeal? and appendiceal tissue removed during the pro-drome. These changes consist of subepithelial round cell infiltration and the presence of multi-nucleated giant cells. The latter is so characteristic that skilled pathologists have predicted the development of rash from their presence in surgical specimens. Similar cells are commonly observed in tissue cultures infected with the measles virus. Cytoplasmic and nuclear inclusions may be seen in epithelial cells. The lesions clinically apparent as Koplik’s spots derive from inflammatory mononuclear cell infiltration of buccal submucous glands and necrosis of focal vesicular lesions of the mucosa.