Environmental Surveillance for Salmonella Typhi and its Association With Typhoid Fever Incidence in India and Malawi

Christopher B. Uzzell, Dilip Abraham, Jonathan Rigby, Catherine M. Troman, Satheesh Nair, Nicola Elviss, Lalithambigai Kathiresan, Rajan Srinivasan, Veeraraghavan Balaji, Nicolette A. Zhou, John Scott Meschke, Jacob John, Gagandeep Kang, Nicholas Feasey, Venkata Raghava Mohan, Nicholas C. Grassly*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Background. Environmental surveillance (ES) for Salmonella Typhi potentially offers a low-cost tool to identify communities with a high burden of typhoid fever. Methods. We developed standardized protocols for typhoid ES, including sampling site selection, validation, characterization; grab or trap sample collection, concentration; and quantitative PCR targeting Salmonella genes (ttr, staG, and tviB) and a marker of human fecal contamination (HF183). ES was implemented over 12 months in a historically high typhoid fever incidence setting (Vellore, India) and a lower incidence setting (Blantyre, Malawi) during 2021–2022. Results. S. Typhi prevalence in ES samples was higher in Vellore compared with Blantyre; 39/520 (7.5%; 95% confidence interval [CI], 4.4%–12.4%) vs 11/533 (2.1%; 95% CI, 1.1%–4.0%) in grab and 79/517 (15.3%; 95% CI, 9.8%–23.0%) vs 23/594 (3.9%; 95% CI, 1.9%–7.9%) in trap samples. Detection was clustered by ES site and correlated with site catchment population in Vellore but not Blantyre. Incidence of culture-confirmed typhoid in local hospitals was low during the study and zero some months in Vellore despite S. Typhi detection in ES. Conclusions. ES describes the prevalence and distribution of S. Typhi even in the absence of typhoid cases and could inform vaccine introduction. Expanded implementation and comparison with clinical and serological surveillance will further establish its public health utility.

Original languageEnglish
Pages (from-to)979-987
Number of pages9
JournalJournal of Infectious Diseases
Issue number4
Publication statusPublished - 15 Apr 2024

Bibliographical note

Publisher Copyright:
© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.


  • India
  • Malawi
  • Salmonella Typhi
  • typhoid fever
  • typhoid-paratyphoid vaccines
  • wastewater surveillance


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