Diphtheria in the United States in 1956

Abstract

D URING the autumn of 1955 and the early winter of 1955-56, diphtheria occurred in the Nation with a frequency not witnessed for a number of years. Fear of a definite resurgence was aroused when outbreaks occurred in areas which had been almost entirely free of the disease for extended periods. The particularly high incidence of the disease in the southeastern States has been described in a previous report (1) prepared at the close of 1955. It is the purpose of this paper briefly to summarize the United States diphtheria experience in 1956. Data on the occurrence of diphtheria cases and deaths were obtained primarily from publications of the Public Health Service's National Office of Vital Statistics, Morbidity and Mortality Weekly Reports and their annual supplements and Vital Statistics of the United States. More detailed information was obtained from current communicable disease reports prepared by States for internal use and from the annual communicable disease statistics published by most States. Additional details were collected by personnel of the Communicable Disease Center in connection with field assignments which dealt directly or indirectly with diphtheria. The assembling and review of such data are continuing functions of the Surveillance Section of the Center. The occurrence of diphtheria in 1955 and 1956, by weeks, is given in figure 1, and the States contributing heavily to the weekly peaks are also indicated. During the first half of 1956 diphtheria incidence continued to be relatively high and was above that of the preceding year in about two-thirds of all weeks. Following the seasonal low, however, the expected pattern of early increase of diphtheria cases in the southern States did not develop to the usual extent. Incidence remained well below that of 1955 throughout the fall and winter, and at the close of the year 1,581 cases had been tentatively reported, compared with 2,039 cases in 1955. Data for 1956 in figures 2 and 3 and table 1 are also preliminary. Although final figures for 1956 are now available, they do not alter the pattern or change the conclusions since they change the total by less than 1 percent. This 22 percent decrease in the incidence of diphtheria restores somewhat the trend of the last decade. After the last increase in reported diphtheria in 1945 there was a fairly steady decline at about 25 percent per year until 1953. In this year the decrease was only 20 percent. In 1954 it was 13 percent and in 1955 only 3 percent. The small drop in cases for the calendar year does not give as clear a picture as the statistics for the disease years. For the disease season of 1955-56, there was actually a 12 percent increase over the disease year 1954-55. The decline in cases in the calendar year of 1956 was due almost entirely to decreases in the last half of the year and in the southeastern States. In figure 2 and table 1, diphtheria morbidity rates are shown by standard geographic divisions and by States for 1949-56. The areas showing the greatest decline in 1956 were the South Atlantic and East South Central States. Small decreases, or essentially no change, occurred in all other divisions except the East North Central and the Mountain States, which showed increases of 0.6 cases per 100,000 population. The increased rate in the East North Central division is almost entirely due to increases in Dr. Moore is chief of the Diphtheria Unit, Surveillance Section, Communicable Disease Center, Public Health Service, Atlanta, Ga.