Studies of the Acute Diarrheal Diseases: IX A. Shigella dysenteriae Infections among Institutional Inmates

Abstract

Two groups in an institution for the mentally defective were followed for 20 months. The average populations were respectively 123 [male][male] and 120 [female][female]. Fecal cultures were obtained at weekly or bi-weekly intervals on all individuals irrespective of clinical condition. Diagnostic cultures were secured at other times on those reported to have diarrhea. 3 Shigella infections were encountered[long dash]Flexner V, Flexner W and Sonne. The first 2 were present at the beginning of the study and spontaneously disappeared from the groups after differing intervals; Sonne persisted tenaciously. Rate of spread varied; in one instance epidemic waves alternated with intervals in which the infection was endemic and spreading very slowly. It was maintained through a continuously changing group of infected individuals. The average annual attack rate for Shigella dysenteriae with clinical manifestations was 16 per 100 [male][male] and 33 per 100 [female][female]. The total known infections were respectively 89 and 115 per 100 inmates per annum. Thus the minimal carrier incidence rates were 73 and 82% per annum. Incidence of diarrheal disorders and of all Shigella infections varied inversely with age. This was related in part to variation in the periods of residence in the institution. The infection rates among those newly admitted was high. Clinical disease was usually associated with Flexner infections but only 16% of all Sonne invasions had associated diarrheal diseases. Clinical manifestations were limited chiefly to 1st infections; symptoms were rare in 2d invasions and were not observed with any of the 14 3d attacks. The observed crude ratios of prevalence of clinical infection to all carrier states were: 1:7 for Flexner and 1:24 for Sonne. Sonne infections occurred with equal frequency among those previously infected with S. dysenteriae (Flexner) and those who had had no known recent infection with these organisms.