Epidemiology and Infection

Risk factors for typhoid fever in an endemic setting, Karachi, Pakistan

S. P. LUBY a1c1, M. K. FAIZAN a1, S. P. FISHER-HOCH a2, A. SYED a1, E. D. MINTZ a3, Z. A. BHUTTA a4 and J. B. MCCORMICK a1
a1 Community Health Sciences Department, Aga Khan University, Karachi, Pakistan
a2 Pathology Department, Aga Khan University, Karachi, Pakistan
a3 Foodborne and Diarrheal Diseases Branch, National Center for Infectious Disease, United States Centers for Disease Control and Prevention, Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA
a4 Pediatrics Department, Aga Khan University, Karachi, Pakistan


We conducted a study to evaluate risk factors for developing typhoid fever in a setting where the disease is endemic in Karachi, Pakistan. We enrolled 100 cases with blood culture-confirmed Salmonella typhi between July and October 1994 and 200 age-matched neighbourhood controls. Cases had a median age of 5·8 years. In a conditional logistic regression model, eating ice cream (Odds ratio [OR]=2·3; 95% confidence interval [CI] 1·2–4·2, attributable risk [AR]=36%), eating food from a roadside cabin during the summer months (OR=4·6, 95% CI 1·6–13·0; AR=18%), taking antimicrobials in the 2 weeks preceding the onset of symptoms (OR=5·7, 95% CI 2·3–13·9, AR=21%), and drinking water at the work-site (OR=44·0, 95% CI 2·8–680, AR=8%) were all independently associated with typhoid fever. There was no difference in the microbiological water quality of home drinking water between cases and controls. Typhoid fever in Karachi resulted from high-dose exposures from multiple sources with individual susceptibility increased by young age and prior antimicrobial use. Improving commercial food hygiene and decreasing unnecessary antimicrobial use would be expected to decrease the burden of typhoid fever.

(Accepted October 28 1997)

c1 Corresponding author: Dr S. P. Luby, Community Health Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, Pakistan.