Highly Pathogenic Avian Influenza A(H5N6) Virus Clade 2.3.4.4h in Wild Birds and Live Poultry Markets, Bangladesh

H ighly pathogenic avian infl uenza (HPAI) A(H5) viruses were identifi ed in 1996 in a goose from Guangdong, China, and the evolution of the hemagglutinins (HAs) of these A/goose/Guangdong/1/96 (Gs/GD) lineage viruses has given rise to multiple genetically distinct phylogenetic clades (1).The emergence of HA clade 2.3.4.4 viruses was associated with several different virus subtypes, including H5N6 (2).As of March 2021, a total of 29 laboratory-confi rmed human cases of H5N6 viruses have been reported from China, and 9 patients have died (3).Clade 2.3.4.4 H5N6 viruses have subsequently evolved, requiring further clade designations.Clade 2.3.4.4h viruses are found in China, Laos, and Vietnam (4).In December 2019 and January 2020, 2.3.4.4 H5N6 viruses were isolated from dead migratory whooper swans (Cygnus cygnus) and mute swans (Cygnus olor) in Xinjiang, western China (5).In April 2021, the same virus was detected in migratory birds in Mongolia (6).In Bangladesh, HPAI A(H5) viruses have been in circulation since 2008; the predominant clades found are 2.2.2 and 2.3.2.1a.HPAI A(H5N6) clade 2.3.4.4b viruses were identifi ed in domestic poultry in Bangladesh in 2016 (7,8).Although the viruses were detected in live poultry markets (LPMs), they did not replace the H5N1 viruses in circulation, and as of April 2021, there have been no more reports of H5N6 virus detection (9,10).We report a new introduction of clade 2.3.4.4.h viruses that are similar to viruses detected in China (Xinjiang) and Mongolia (5,6), suggesting that migratory birds of the Central Asian fl yway introduced this virus into Bangladesh. The StudySince 2015, our active surveillance in Bangladesh has been ongoing in both LPMs and Tanguar Haor, a wetlands area where local domestic ducks are reared and where birds winter during the migratory season (Appendix, Table 1, https://wwwnc.cdc.gov/EID/article/27/9/21-0819-App1.pdf).We collected H5N6 virus-positive oropharyngeal and cloacal swabs from 2 apparently healthy wild birds in Baghmara, Tanguar Haor: a ferruginous duck on January 19, 2020, and a common pochard on January 20, 2020.We also obtained positive fecal samples from wild mallard ducks on January 26, 2020, in Puran Gao, Tanguar Haor.The next day, we obtained positive oropharyngeal and cloacal swabs from apparently healthy Khaki Campbell ducks located on various farms in Golabari, Tanguar Haor (Appendix Table 1).On February 18, 2020, ≈3 weeks after detection of H5N6 virus in Tanguar Haor, an apparently healthy mallard duck