Typhoid Fever and Nontyphoid Salmonellosis | CDC EID

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Volume 16, Number 9–September 2010
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Typhoid Fever and Invasive Nontyphoid Salmonellosis, Malawi and South Africa
Nicholas A. Feasey, Brett N. Archer, Robert S. Heyderman, Arvinda Sooka, Brigitte Dennis, Melita A. Gordon, and Karen H. Keddy
Author affiliations: Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi (N.A. Feasey, R.S. Heyderman, B. Dennis); National Institute for Communicable Diseases, Johannesburg, South Africa (B.N. Archer, A. Sooka, K.H. Keddy); University of the Witwatersrand, Johannesburg (K.H. Keddy); and University of Liverpool, Liverpool, UK (M.A. Gordon)

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Abstract
To determine the prevalence of invasive nontyphoid salmonellosis and typhoid fever in Malawi and South Africa, we compared case frequency and patient age distribution. Invasive nontyphoid salmonellosis showed a clear bimodal age distribution; the infection developed in women at a younger age than in men. Case frequency for typhoid fever was lower than for salmonellosis.
Invasive nontyphoid salmonellosis (iNTS) was first described as an AIDS-related illness in Africa and the United States in the 1980s. Although incidence in industrialized countries declined, nontyphoid Salmonella (NTS) spp. serovars (predominantly S. enterica serovars Typhimurium and Enteritidis) remain a common cause of bloodstream and focal infection in sub-Saharan Africa for adults with HIV infection and children with HIV, malaria, and malnutrition. iNTS has a strong seasonal pattern in adults and children. In addition, epidemics of iNTS have been described as associated with the emergence of multidrug resistance in Malawi (1). Similarly, multidrug resistance is well recognized in iNTS in South Africa (www.nicd.ac.za/pubs/survbull/2010/CommDisBullMay10_Vol0802.pdf). Death rates are 20%–25% among adults and children (1). In sub-Saharan Africa, transmission is thought most likely to be between humans, and no food or animal source has been found, although epidemiologic data remain sparse (2).

In comparison to iNTS, S. enterica serovar Typhi is a highly adapted, invasive, human-restricted pathogen that in the 19th century caused considerable illness and death in the United States and Europe but now has the greatest impact in developing countries. In sub-Saharan Africa, perhaps surprisingly, typhoid fever is not associated with HIV among adults (3).

Regional data on the demography and prevalence of both iNTS and S. Typhi for sub-Saharan Africa are incomplete (4). Estimates of incidence of iNTS among children, 175–388/100,000 (5–7), and among adult HIV-prevalent cohorts, 2,000–8,500/100,000 (8–10), have been made separately, in different locations, giving no overall demographic picture. Estimates of the incidence of typhoid fever have relied on limited available data from sub-Saharan Africa (11). Although typhoid is usually regarded as an illness of school-age (>5 years of age) children and young adults, there is considerable heterogeneity; some sites in Asia report high incidences of typhoid fever among children <5 years of age (12). We compared case frequency and patient age distribution for the predominant types of invasive salmonellosis among febrile patients of all ages treated at our 2 centers in 2 regions in sub-Saharan Africa, Malawi and South Africa, before 2004.


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