The epidemiology of acute rheumatic fever 1950–1964

Abstract 1. 1. There has been a steady fall in the gross number of deaths each year from acute rheumatic fever and its sequelae during the past several decades, as well as in the age adjusted death rates. The data suggest that the rate of fall in death rates from acute rheumatic fever itself has been greater than that from chronic rheumatic heart disease. This is true, to varying degrees, for both sexes and in all racial groups. 2. 2. Morbidity data are poor, but it is probably justifiable to infer from them that the incidence of acute rheumatic fever has also fallen. 3. 3. The evidence associating acute rheumatic fever with hemolytic streptococcus Lancefleld group A is overwhelming. Acute rheumatic fever follows in about 3 per cent of patients whose streptococcal illness is characterized by pharyngeal exudate, a temperature in excess of 101 °F, a polymorphonuclear leucocytosis of more than 12,000, a typable hemolytic group A streptococcus and a considerable rise of antistreptolysin O litre. However, rheumatic fever can, not infrequently, follow a silent streptococcal illness. 4. 4. The fact that rheumatic fever only develops in 3 per cent of a group of people who apparently have an identical precipitating illness suggests that differences in the host may contribute to the pathogenesis of the disease. Persons of blood group O may be a little less likely to develop rheumatic carditis than those in the other ABO groups, but non-secretors of these substances are probably more susceptible than secretors; possibly liability is also unequally distributed in respect of Rh and MN blood groups. 5. 5. The sexes are equally prone to develop acute rheumatic fever, but the female is the more susceptible to Sydenham's chorea and in some countries (e.g. England and Wales) she is the more likely to die of chronic rheumatic heart disease. In the United States and in England and Wales the crude death rates from rheumatic disease of the aortic valve are twice as high in males as in females. 6. 6. The disease, uncommon before the age of 5, is most likely to occur in school children and decreases steadily in frequency after puberty. The probability of developing it is enhanced if the antistreptolysin O titre, previous to the precipitating streptococcal infection, is high. 7. 7. The risk of acute rheumatic fever is greatest where opportunities for infection are high, in the towns against the country, the large family against the small and where there is bad housing and undernutrition. It is not confined to temperate zones and is known to be common in tropical areas of South America, some Caribbean Islands and on the Indian sub-continent. In the United States, with the curious and unexplained exception of a high incidence and mortality in the Mountain States, it is closely related to population density. 8. 8. The steady regression of acute rheumatic fever, and of its sequelae, as health problems in the U.S.A., is probably a consequence of the many factors which make repeated and rapidly spreading epidemics of streptococcal disease less likely to occur. It may be that certain physical properties of the organism, upon which its virulence depends, are determined by its rate of spread from one individual to another. 9. 9. Reasons for the changing epidemiological features may include such different factors as the slow but steady increase in the purchasing power of the average pay packet; modern housing; the revolution in school design in the 20th century; clean milk; and most recently, the ready availability of antibiotics.