Pandemic potential of highly pathogenic avian influenza clade 2.3.4.4 A(H5) viruses

Abstract

Summary The panzootic caused by A/goose/Guangdong/1/96‐lineage highly pathogenic avian influenza (HPAI) A(H5) viruses has occurred in multiple waves since 1996. From 2013 onwards, clade 2.3.4.4 viruses of subtypes A(H5N2), A(H5N6), and A(H5N8) emerged to cause panzootic waves of unprecedented magnitude among avian species accompanied by severe losses to the poultry industry around the world. Clade 2.3.4.4 A(H5) viruses have expanded in distinct geographical and evolutionary pathways likely via long distance migratory bird dispersal onto several continents and by poultry trade among neighboring countries. Coupled with regional circulation, the viruses have evolved further by reassorting with local viruses. As of February 2019, there have been 23 cases of humans infected with clade 2.3.4.4 H5N6 viruses, 16 (70%) of which had fatal outcomes. To date, no HPAI A(H5) virus has caused sustainable human‐to‐human transmission. However, due to the lack of population immunity in humans and ongoing evolution of the virus, there is a continuing risk that clade 2.3.4.4 A(H5) viruses could cause an influenza pandemic if the ability to transmit efficiently among humans was gained. Therefore, multisectoral collaborations among the animal, environmental, and public health sectors are essential to conduct risk assessments and develop countermeasures to prevent disease and to control spread. In this article, we describe an assessment of the likelihood of clade 2.3.4.4 A(H5) viruses gaining human‐to‐human transmissibility and impact on human health should such human‐to‐human transmission occur. This structured analysis assessed properties of the virus, attributes of the human population, and ecology and epidemiology of these viruses in animal hosts.

Avian Influenza A Virus Infects Swine Airway Epithelial Cells without Prior Adaptation

“…Moreover, evidence of globally widespread H9N2 viruses acquired key mammalian adaptation markers in the past decade represents a genuine threat for humans [ 6 , 7 ]. While avian influenza A viruses (IAVs) have the ability to infect different mammalian species even marine mammals [ 8 , 9 , 10 ], there is a need to investigate the zoonotic potential of avian influenza viruses in pigs.…”

Genetic diversity, phylogeography, and evolutionary dynamics of highly pathogenic avian influenza A (H5N6) viruses

“…In the ML tree of the HA gene, clade 2.3.4.4 H5 subtype viruses had evolved into four distinct genetic subclades. Following a previous study ( Yamaji et al. 2020 ), four subclades were designated with Group A (a group represented by A/gyrfalcon/Washington/41088-6/2014), Group B (a group represented by A/Fujian-Sanyuan/21099/2017), Group C (a group represented by A/Hubei/29578/2016), and Group D (a group represented by A/Sichuan/26221/2014).…”

“…In 2014, a new clade of H5Nx viruses (2.3.4.4) emerged, this clade viruses had acquired an unprecedented number of neuraminidase (NA) subtypes, including N2, N3, N6, and N8 ( Smith et al. 2015 ; Yamaji et al. 2020 ), which were detected in domestic and wild birds in Asia, North America, and Europe.…”

“…Subsequently, those novel H5N6 variants disseminated to Switzerland, Iran, Finland, Sweden, Germany, the United Kingdom, and Denmark ( Poen et al. 2019 ; Yamaji et al. 2020 ).…”

The pathogenesis of a North American H5N2 clade 2.3.4.4 group A highly pathogenic avian influenza virus in surf scoters (Melanitta perspicillata)

“…It was the most common of the 4 clade 2.3.4.4 variants detected in domestic birds and was the only variant identified in North American surveillance samples from wild birds after the outbreak [ 45 ], although it has not been detected in North America since 2016. However, sporadic outbreaks of a related H5N2 reassortants continue to be detected in poultry in Taiwan [ 46 ]. Therefore, there may be some fitness advantage to this gene constellation in domestic birds.…”