Repeated SARS-CoV-2 Introductions with Limited Local Establishment in Bangladesh, 2020-2025

A study analyzed SARS-CoV-2 genomes collected in Bangladesh between March 2020 and July 2025 to understand how the virus spread in a country with limited sequencing capacity. Researchers identified 361 lineage introduction events, with 51.8% leaving only a single sequenced genome with no further transmission detected. India and the Persian Gulf were the dominant sources of infection, while East Asia and Southeast Asia had lower proportions than expected. The research revealed 18 mutations enriched in Bangladeshi genomes, of which 53 arose after the variant's arrival in the country. The Spike G446V mutation arose locally in 17 of 19 lineages and reached 91.8% of genomes in an imported Delta lineage. The study demonstrates that viral importation determined which variants circulated in Bangladesh, while local evolution determined their behavior within the country.