Symptomatic and Asymptomatic Shigella Infection in Dhaka, Bangladesh: Findings from Hospital and Community Surveillance, 2025

In low- and middle-income countries, Shigella is an important cause of diarrheal disease, and infections often occur without clinical symptoms. Asymptomatic individuals may act as reservoirs for ongoing community transmission, but their contribution to the overall burden remains poorly understood. This analysis aimed to generate evidence on asymptomatic and symptomatic Shigella infection in Dhaka, Bangladesh, to enlighten surveillance and prevention strategies. We analyzed data from the hospital-based diarrheal disease surveillance system (DDSS) of icddr,b Dhaka Hospital and asymptomatic participants from the community, covering January to December 2025. Stool or rectal swabs were cultured and serotyped for Shigella species. In 2025, Shigella was detected in 68 (2.5%, 95% CI: 2.0–3.1%) among 2738 diarrheal patients, compared with 51 of 784 asymptomatic community participants (6.5%, 95% CI: 5.0–8.4%) and this difference was significant (p value < 0.001). In both groups, participants aged 5–17 years had the highest positivity (hospital 6.2% and community 12.1%). Positivity was also significantly higher in the community for both males (7.6% vs. 2.8%, p < 0.001) and females (5.3% vs. 2.1%, p = 0.001). S. flexneri was predominant in both populations (64.7% and 58.8%). S. sonnei was more common among hospital patients (29.4% vs. 5.9%), whereas S. boydii was more common among community participants (31.4% vs. 4.4%). Hospital positivity was observed throughout the year, with no clear seasonal peak, whereas community positivity climbed in October and December. Integrated hospital and community surveillance may provide a more complete understanding of Shigella transmission and guide prevention strategies.