Measles Virus Genomic Surveillance Gaps during a Nationwide Outbreak, Bangladesh, 2026

Bangladesh reported a nationwide measles outbreak in April 2026 involving over 19,000 suspected cases, despite high reported first-dose vaccine coverage ([≥]95%). We assessed whether publicly available molecular data could support epidemiologic interpretation of this resurgence and evaluated broader sequence sharing practices across South Asia. We analyzed public outbreak reports, WHO/UNICEF Estimates of National Immunization Coverage (WUENIC), PubMed indexed literature, and NCBI GenBank records from nine regional countries. Public sequence visibility across the region was highly uneven. While India and Pakistan associated records dominated the public dataset, only 32 Bangladesh origin records were retrieved, and notably, none were collected after 2019. The sole 2026 Bangladesh linked molecular record was a travel associated genotype B3 genome isolated in Australia (PZ189094.1). Its closest public N450 relative was a contemporaneous Pakistan sequence (2-nucleotide difference). The historical Bangladesh sequences were more distant, precluding robust phylogenetic inference regarding local viral persistence, cross-border importation, or transmission direction. Immunization data revealed a high regional baseline but highlighted subnational vulnerability and a significant pandemic era coverage collapse in neighboring Myanmar. The absence of timely, publicly available genomic data during the critical early months of the outbreak highlights a severe genomic surveillance gap. Public molecular records were historically sparse and insufficient to reconstruct outbreak transmission dynamics. To support elimination goals, establishing targeted sequencing pipelines, enforcing minimum metadata standards, and ensuring rapid public data deposition are urgently needed. Keywords: measles; Bangladesh; South Asia; genomic surveillance; molecular epidemiology; immunization coverage