Two Decades of Highly Pathogenic Avian Influenza in Bangladesh: Spatiotemporal Patterns, Seasonality, and Emerging Wildlife Detections, 2007-2025

Highly pathogenic avian influenza (HPAI) has recurred in Bangladesh's poultry sector since 2007, with periodic detections in wild birds since 2017. This study presents a reproducible spatiotemporal analysis of the full official WOAH WAHIS surveillance record for Bangladesh, 2007-2025, combined with climate (NASA POWER) and poultry-density (FAO GLW4) covariates. Key findings: (1) Bangladesh reported 564 new HPAI outbreaks across 8 divisions/localities, 2007-2025, with Dhaka division carrying 47% of the national burden; (2) outbreaks are strongly seasonal — 525 of 563 division-resolved outbreaks (93.3%) occurred in the January-June dry/cool semester, confirmed by a negative-binomial regression controlling for division (p<0.05 for temperature, humidity, and precipitation); (3) a report-level reconstruction of the largest tracked epidemic (2007-2013, WAHIS event 192) reveals two distinct peaks — April 2008 and March 2011 — invisible in standard semester-aggregated data; (4) the most recent record (April 2025) is H5N1 in a captive Serval in Narayanganj, a One Health signal distinct from the historical poultry-sector pattern. Data source: WOAH World Animal Health Information System (WAHIS), publicly available official animal-health surveillance data, accessed August 2026. All analysis code, cleaned datasets, and figures are available at: https://github.com/khalilurrrahmanridoykhan/bangladesh-avian-influenza-2007-2025