Epidemiology of three cases of severe diphtheria in Finnish patients with low antitoxin antibody levels

During the 1990-1998 diphtheria epidemic in the newly independent states of the former Soviet Union, more than 150,000 infections and 5,000 deaths occ urred. During this period, more than 10 million trips were made from Finlan d to Russia or vice versa. This resulted in only 10 cases of diphtheria in Finland. There was no secondary spread to healthcare workers or other close contacts. Three patients had severe respiratory tract diphtheria. All thre e were middle-aged men who had made a short visit to Russia, during which t ime they had intimate contact with local women. These findings suggest diph theria was transmitted mainly by direct saliva contact. All patients with s evere diphtheria had a nonprotective level of antitoxin antibodies during t he first days of the disease. Only the patient whose antibody titre rose ra pidly to a protective level (>1 IU/ml) had an uncomplicated recovery. The o ther two, one of whom died, had myocarditis and severe polyneuropathy.