Abstract
Highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype are enzootic in poultry populations in different parts of the world, and have caused numerous human infections in recent years, particularly in Egypt. However, no sustained human-to-human transmission of these viruses has yet been reported. We tested nine naturally occurring Egyptian H5N1 viruses (isolated in 2014–2015) in ferrets and found that three of them transmitted via respiratory droplets, causing a fatal infection in one of the exposed animals. All isolates were sensitive to neuraminidase inhibitors. However, these viruses were not transmitted via respiratory droplets in three additional transmission experiments in ferrets. Currently, we do not know if the efficiency of transmission is very low or if subtle differences in experimental parameters contributed to these inconsistent results. Nonetheless, our findings heighten concern regarding the pandemic potential of recent Egyptian H5N1 influenza viruses.
Highlights
Pathogenic avian influenza (HPAI) viruses of the H5N1 subtype are enzootic in poultry populations in different parts of the world, including several Southeast Asian countries and Egypt
Highly pathogenic avian influenza (HPAI) H5N1 influenza viruses isolated from household poultry in 2014 and 2015 (Supplementary Table S1) for their respiratory droplet transmissibility in ferrets
Avian influenza viruses including HPAI H5N1 viruses typically bind to sialic acids linked to galactose by an α2,3-linkage (Siaα[2,3] Gal; expressed on epithelial cells of duck intestine)[10]
Summary
Pathogenic avian influenza (HPAI) viruses of the H5N1 subtype are enzootic in poultry populations in different parts of the world, including several Southeast Asian countries and Egypt. It is unclear whether the high number of human HPAI H5N1 infections in Egypt in 2014–2015 reflects socioeconomic changes resulting in increased contact between people and infected animals or if genetic changes in the virus have increased its predilection for human infections. The HPAI H5N1 viruses were introduced into Egyptian poultry populations in 2006 as descendants of the Qinghai Lake lineage of H5N1 viruses, which belong to subclade 2.2 of the WHO classification system of HPAI H5N1 influenza viruses. Almost all recent human cases in Egypt have been caused by viruses of subclades 2.2.1 and 2.2.1.2. Given that HPAI H5N1 viruses in Egypt evolve rapidly and have caused a substantial number of human infections, we here characterized the respiratory droplet transmissibility of nine Egyptian HPAI H5N1 influenza viruses in ferrets
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