Secular Trends in the United States
Globally, diphtheria was once a major cause of morbidity and mortality
among children. In England and Wales during the 1930s, diphtheria was among
the top three causes of death for children younger than 15 years of age.
During the 1920s in the United States, 100,000–200,000 cases of diphtheria
(140–150 cases per 100,000 population) and 13,000–15,000 deaths were
reported each year. In 1921, a total of 206,000 cases and 15,520 deaths
were reported. The number of cases gradually declined to about 19,000 in
1945 (15 per 100,000 population). A more rapid decrease began with the
widespread use of diphtheria toxoid in the late 1940s.
From 1970 through 1979, an average of 196 cases per year were reported.
This included a high proportion of cutaneous cases from an outbreak in
Washington State. Beginning in 1980, all cutaneous cases were excluded from
reporting. Diphtheria was seen most frequently in Native Americans and
persons in lower socioeconomic strata.
From 1980 through 2011, 55 cases of diphtheria were reported in the United
States, an average of 1 or 2 per year (range, 0–5 cases per year). Only 5
cases have been reported since 2000.
Of 53 reported cases with known patient age since 1980, 34 (64%) were in persons 20 years of age or older; 41% of cases were among persons 40 years of age or older. Most cases have occurred in unimmunized or inadequately immunized persons. The current age distribution of cases corroborates the finding of inadequate levels of circulating antitoxin in many adults (up to 60% with less than protective levels). Although diphtheria disease is rare in the United States, it appears that toxigenic Corynebacterium diphtheriae continues to circulate in areas of the country with previously endemic diphtheria. In 1996, 8 isolates of toxigenic C. diphtheriae were obtained from persons in a Native American community in South Dakota. None of the infected persons had classic diphtheria disease, although five had either pharyngitis or tonsillitis.
The presence of toxigenic C. diphtheriae in this community is a good reminder for providers not to let down their guard against this organism.
Diphtheria continues to occur in other parts of the world. A major epidemic of diphtheria occurred in countries of the former Soviet Union beginning in 1990. By 1994, the epidemic had affected all 15 Newly Independent States (NIS). More than 157,000 cases and more than 5,000 deaths were reported. In the 6 years from 1990 through 1995, the NIS accounted for more than 90% of all diphtheria cases reported to the World Health Organization (WHO) from the entire world. In some NIS countries, up to 80% of the epidemic diphtheria cases have been among adults. The outbreak and the age distribution of cases are believed to be due to several factors, including a lack of routine immunization of adults in these countries. Globally, reported cases of diphtheria have declined from 11,625 in 2000 to 4,880 cases in 2011.
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