Materials and methods
Study Site
Surveillance was conducted in administrative areas (currently 8) designated as “Divisions” (Bibhag) with a total of 64 dis- tricts (Zilla) and 492 subdistricts (Upazila). In May 2014, the icddr,b and the Institute of Epidemiology, Disease Control, and Research (IEDCR) collaboratively started the diarrheal disease surveillance in 10 hospitals. Surveillance was interrupted be- tween January and May 2016 due to a gap in funding. From May 2016, surveillance was expanded to additional 12 facilities
focusing on cholera surveillance. A total of 22 surveillance sites (13 districts, 6 subdistricts, 2 tertiary-level hospitals, and the Bangladesh Institute of Tropical and Infectious Disease [BITID]) were established across 21 different districts (Figure 1). We selected sentinel surveillance sites based on reports of acute watery diarrhea and cholera (including analyses of data from the national District Health Information Software v2 database) from the Directorate General of Health Services and previously published cholera surveillance studies [6].
Diarrhea Case Definition
Surveillance was carried out in all age groups; however, different case definitions for those under 2 months of age and those older than or equal to 2 months are as follows:
⦁ Diarrhea cases (age <2 months): Changed stool habit from usual pattern in terms of frequency (more than the usual number of purgings) or nature of stool (more water than fecal matter).