Changes in enteric fever trends during the COVID-19 pandemic from the Surveillance for Enteric Fever in Asia Project: a cross-sectional study

Background: The Surveillance for Enteric Fever in Asia Project (SEAP) conducted blood culture surveillance for Salmonella enterica serotype Typhi (S. Typhi) and Paratyphi (S. Paratyphi) to provide an evidence base for prevention and control measures in Bangladesh, Nepal, and Pakistan. Methods: From October 2020 to September 2022, we conducted prospective clinical surveillance and retrospective laboratory surveillance at health facilities in Dhaka, Bangladesh; Kathmandu and Kavrepalanchok, Nepal; and Karachi, Pakistan. Patients were eligible if they were outpatients with three or more days of fever in the last week. In Nepal and Pakistan, inpatients were eligible if they had suspected or confirmed enteric fever; in Bangladesh, only inpatients with confirmed enteric fever were enrolled. Patients with blood culture–confirmed enteric fever identified by hospital laboratories and laboratory network sites were also enrolled. Patients completed interviews and medical records were reviewed and abstracted. All enrolled patients had blood cultures performed. Antibiograms were performed to characterize drug sensitivity. We summarized the data descriptively. Findings: A total of 17,593 patients were enrolled from 19 facilities. Of these, 8410 patients had culture-confirmed enteric fever. Case counts in all countries decreased in the early stages of the COVID-19 pandemic, but increased over time in Bangladesh and Pakistan. Case counts remained low throughout the study period in Nepal. In all countries, typhoid was more common than paratyphoid; the proportion of paratyphoid cases ranged from 8.4% in Pakistan to 16% in Nepal. Extensively drug-resistant typhoid was common in Pakistan (69%), but was not detected in Bangladesh or Nepal. Interpretation: Cases of enteric fever decreased during the COVID-19 pandemic, though it is not clear how much of this decrease relates to true changes in transmission versus health-seeking behavior. Funding: This project was funded by the Gates Foundation through INV-008335.