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.
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. 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. Only 33 cases of diphtheria were reported in the United States between 1981 and 1990. The last reported case of diphtheria in Maryland occurred in 1973. In 1970, there were 13 reported cases in Maryland.