Diphtheria

Diphtheria

Current Case Definition for Surveillance

The current clinical case definition of diphtheria for surveillance purposes is: "An upper respiratory tract illness characterized by sore throat, low-grade fever, and an adherent membrane of the tonsils(s), pharynx, and/or nose." Beginning in 1980, cutaneous diphtheria was excluded from reporting in the United States. A laboratory criterion for diagnosis involves either isolation of the organism from a clinical specimen or a histopathologic diagnosis of diphtheria. A confirmed case is one that is clinically compatible and either laboratory confirmed or epidemiologically linked to a laboratory-confirmed case.

Immunization

The diphtheria toxoid was developed in 1921, came into use in the early 1930's, and into widespread use in the United States in diphtheria-pertussis-tetanus vaccine (DTP) from the mid 1940's. While adequate studies of clinical efficacy are lacking, a protective level of antitoxin is reached in over 95% of young children following the primary series of four toxoid doses.

Most individuals have antitoxin levels below optimal levels ten years after the last dose. Immunization is required by Maryland law for children in preschool programs and in kindergarten through the twelfth grade, and booster doses are recommended every ten years. Based on the 1998/99 retrospective kindergarten survey, an estimated 78% of children in Maryland had received four doses of DTP by 24 months of age (60% in the 1988/89 survey).

Historical Trends (see graphs below)

At one time, respiratory diphtheria was common, occurred primarily in children, and was one of the major causes of infant and child mortality in the United States. In the 1920's approximately 150,000 cases of diphtheria were reported annually (140 cases per 100,000 population). Only 33 cases of diphtheria were reported in the United States between 1981 and 1990. From the time data collection began, the case fatality rate of approximately 9% overall, and nearly 20% in those under five or over 40 years of age, has remained essentially unchanged.