Trends in Age Distribution of Diphtheria in the United States

Abstract

adults. The present study has been carried out for the purpose of determining the validity of the statement that diphtheria is actually becoming more common in adults. It was felt that a study of the trends of both morbidity and mortality by age groups over a period of years in certain States and cities would give a fairly accurate estimate of such a change if one actually has occurred. Only a limited number of States and cities have published, or have available, tabulations of reported cases of diphtheria by age groups for a sufficiently long period of time to permit a study of trends. Those with data covering a period of 20 years or more include five northern States, three of which have a high proportion of urban population (Massachusetts, Connecticut, and New Jersey) and two which are predominantly rural (Minnesota and Kansas). Two are typical southern States (North Carolina ancd Alabama) and one borderline (Maryland). In addition to these, data are available for one western State (California) and for two cities, the District of Columbia and Baltimore. The trend of distribution in upper New York State has been reported by Ingraham and Korns (1) and is not repeated here. The 5-year period ending in 1944 was made the endpoint of the study because there are no dependable estimates of populations by age groups since the 1940 census. No separation was made of cases and deaths by race except for Alabama. Data for Maryland, used in this study, are exclusive of Baltimore. When calculating morbidity rates, all cases of unknown age were distributed according to the percentage distribution of cases of known age. In this report the trend of morbidity and mortality will be emphasized more than any differences in rates in one