Outbreaks of highly pathogenic avian influenza H5N1 clade 2.3.2.1c in hunting falcons and kept wild birds in Dubai implicate intercontinental virus spread

Highly pathogenic avian influenza viruses (HPAIV) of subtype H5N1 have continued to perpetuate with divergent genetic variants in poultry within Asia since 2003. Further dissemination of Asian origin-derived H5 HPAI viruses to Europe, Africa and, most recently, to the North American continent, have occurred. We report an outbreak of HPAI H5N1 virus among falcons kept for hunting and other wild bird species bred as falcon prey from Dubai, United Arab Emirates, during fall 2014. The causative agent was identified as avian influenza virus H5N1 subtype, clade 2.3.2.1c, by genetic and phylogenetic analyses. High mortality in infected birds was in accordance with systemic pathomorphological and histological alterations in affected falcons. Genetics analysis showed the HPAI H5N1 of clade 2.3.2.1c is a reassortant in which the PB2 segment was derived from an Asian origin H9N2 virus lineage. The Dubai H5N1 viruses were closely related to contemporary H5N1 HPAI viruses from Nigeria, Burkina-Faso, Romania and Bulgaria. Median-joining network analysis of 2.3.2.1c viruses revealed that the Dubai outbreak was an episode of a westward spread of these viruses on a larger scale from unidentified Asian sources. The incursion into Dubai, possibly via infected captive hunting falcons returning from hunting trips to central Asian countries, preceded outbreaks in Nigeria and other Western African countries. The alarmingly enhanced geographic mobility of clade 2.3.2.1.c and clade 2.3.4.4 viruses may represent another wave of transcontinental dissemination of Asian origin HPAIV H5 viruses, such as the outbreak at Qinghai lake caused by the clade 2.2 ("Qinghai" lineage) in 2005.