Diphtheria in Stockholm, with a theory concerning transmission

Since 1984, diphtheria has been diagnosed in Sweden, mainly among men abusing alcohol. During the first half of 1986, eight cases of diphtheria were discovered in the city of Stockholm. The first three were among men abusing alcohol. The following five cases had no connection with them. These five persons were employed in two companies housed in the same building. The only connection between them was that they ate their lunch at the same restaurant. One alcohol-abusing man had worked temporarily in the kitchen of this restaurant during the week before the five cases of diphtheria arose. He knew one of the first three patients well. A throat swab taken from him a month after the five cases had been diagnosed was negative. It was suspected however, that this man might have been a carrier of Corynebacterium diphtheriae during the week that he worked in the kitchen. Tests for C. diphtheriae antitoxin revealed that the kitchen staff had high antitoxin titres although they lacked a history of basic immunisation. Even so, C. diphtheriae could not be isolated from their throats and it has not been possible to establish the mode of transmission. The most reasonable theory of transmission is that the organism was introduced into the kitchen by the man employed there temporarily and that it was spread by food served in the restaurant. This theory has not been proved but is discussed in order to facilitate future investigations of a similar outbreak.