Salmonellosis in general practice. Observations of cases and their household in Enfield.

Nine hundred and seventeen Salmonella infections in 580 households were confirmed during a laboratory study of diarrhoea in general practices in a large urban area during the years 1953-68. This was an annual incidence of about 2/10,000 population. Salmonellas were found in nearly 2% of new cases of diarrhoea investigated. Plural infections were found in 36% of the households studied and 18% of all contacts examined were shown to be infected. Among these contacts the infection rate was higher for children (24%) than for adults (16%). The duration of infection was longer than 2 months in nearly a quarter of the cases followed up, and intermittent excretion was observed in one-fifth. The commonest serotype was Salmonella typhimurium, but its incidence in the district declined especially after 1964. S. typhimurium infection provoked a severer enteritis but less general symptoms than did other salmonellas. Children were more susceptible than adults to salmonella infection, to illness and to prolonged excretion, but symptoms in index cases were as severe in adults as in children.