Invasive salmonellosis in Malawi.

The incidence of invasive salmonellosis has increased among children and HIV-infected adults in Malawi. This has been associated with the emergence of drug resistance in the non-typhoidal Salmonella serovars Enteritidis and Typhimurium. In contrast, S. Typhi isolates have remained fully sensitive to commonly used antibiotics and the estimated incidence of typhoid fever, although still present, has fallen slightly among both adults and children. Infection with S. Typhi is not closely associated with underlying immunosuppression but it is possible that the non-typhoidal Salmonellae have adapted to the person-person human transmission niche in this frequently immunosuppressed population. The huge burden of invasive salmonellosis in Malawi, the high associated mortality, and the recent emergence of drug resistance emphasise the need for a better understanding of the epidemiology and the need for vaccine development.