Assessing the Role of Typhoid Fever Carriers in Disease Transmission

Abstract

Typhoid fever (enteric fever) remains a major public health problem in many low- and middle-income countries, sustained by fecal–oral transmission of Salmonella enterica serovar Typhi (S. Typhi). While acute symptomatic cases are readily recognized and treated, a smaller but epidemiologically important fraction of infected persons become carriers who intermittently or continuously shed S. Typhi for months to years, often without symptoms. Chronic carriage (commonly defined as shedding ≥12 months) can maintain S. Typhi in human populations, seed outbreaks, and frustrate elimination efforts, particularly where water, sanitation, and hygiene (WASH) systems are weak, and food handling is informal. This review synthesizes current understanding of (i) carrier states and their biological basis (especially gallbladder persistence and biofilm formation), (ii) the relative contribution of carriers to transmission in endemic vs non-endemic settings, (iii) practical approaches for detection and confirmation of carriers, and (iv) interventions to reduce transmission risk ranging from vaccination and WASH improvements to targeted screening and treatment of high-risk groups. We highlight key evidence gaps, including the lack of scalable diagnostics for carriers and limited field data quantifying carrier-attributable transmission under contemporary antimicrobial resistance (AMR) pressures. Keywords: typhoid fever; Salmonella Typhi; chronic carrier; convalescent carrier; WASH; typhoid conjugate vaccine.