Respiratory diphtheria caused by Corynebacterium ulcerans--Terre Haute, Indiana, 1996

Diphtheria is a potentially severe illness; among unvaccinated persons, the case-fatality rate may be 5%-10%, even with appropriate treatment. During 1990-1995, approximately 4000 deaths resulted from the ongoing diphtheria epidemic in the former Soviet Union. In the United States, respiratory diphtheria is rare: during 1980-1995, only 41 cases were reported. Serologic studies in the 1970s and 1980s indicated that 20%-60% of U.S. adults aged > or = 20 years lacked immunity to diphtheria. This report describes a recent case of respiratory diphtheria caused by a toxin-producing strain of Corynebacterium ulcerans. The case occurred in a resident of Indiana, and an investigation by public health authorities indicated that acquisition of the organism occurred locally in the state.