Avian influenza overview April – June 2023

Adlhoch, Cornelia; Fusaro, Alice; Gonzáles, José L.; Kuiken, Thijs; Melidou, Angeliki; Mirinavičiūtė, Gražina; Niqueux, Éric; Ståhl, Karl; Staubach, Christoph; Terregino, Calogero; Baldinelli, Francesca; Broglia, Alessandro; Kohnle, Lisa

doi:10.2903/j.efsa.2023.8191

Cited by 26 publications

(39 citation statements)

References 46 publications

(32 reference statements)

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“…In the summer 2022, this genotype had been detected mainly in European herring gulls in Northern Europe (France, Belgium, the Netherlands, and occasionally in the UK). However, starting from autumn 2022, a southward spread of this genotype to Spain and then Italy, Switzerland, and Austria, followed by an eastward and northward spread to Poland, the Czech Republic, Croatia, Sweden, Norway, and Denmark, was reported ( Adlhoch et al., 2023a , 2023b ). The ongoing and widespread circulation of this genotype in the gull population, with black-headed gulls representing the most affected species since winter 2022–2023, highlights the serious threat posed by this variant to the sea-bird population, with mass mortality events persistently reported in several colonies of gulls and terns from different countries ( Adlhoch et al., 2023a ).…”

Section: Discussionmentioning

confidence: 99%

High pathogenic avian influenza A(H5) viruses of clade 2.3.4.4b in Europe—Why trends of virus evolution are more difficult to predict

Fusaro,

Zecchin,

Giussani

et al. 2024

Virus Evolution

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Since 2016, A(H5Nx) high pathogenic avian influenza (HPAI) virus of clade 2.3.4.4b has become one of the most serious global threats not only to wild and domestic birds, but also to public health. In recent years, important changes in the ecology, epidemiology and evolution of this virus have been reported, with an unprecedented global diffusion and variety of affected birds and mammalian species. After the two consecutive and devastating epidemic waves in Europe in 2020-2021 and 2021-2022, with the second one recognized as one of the largest epidemics recorded so far, this clade has begun to circulate endemically in European wild bird populations. This study used the complete genomes of 1,956 European HPAI A(H5Nx) viruses to investigate the virus evolution during this varying epidemiological outline. We investigated the spatiotemporal patterns of A(H5Nx) virus diffusion to/from and within Europe during the 2020-2021 and 2021-2022 epidemic waves, providing evidence of ongoing changes in transmission dynamics and disease epidemiology. We demonstrated the high genetic diversity of the circulating viruses, which have undergone frequent reassortment events, providing for the first time a complete overview and a proposed nomenclature of the multiple genotypes circulating in Europe in 2020-2022. We described the emergence of a new genotype with gull adapted genes, which offered the virus the opportunity to occupy new ecological niches, driving the disease endemicity in the European wild bird population. The high propensity of the virus for reassortment, its jumps to a progressively wider number of host species, including mammals, and the rapid acquisition of adaptive mutations make the trend of virus evolution and spread difficult to predict in this unfailing evolving scenario.

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Section: Discussionmentioning

confidence: 99%

High pathogenic avian influenza A(H5) viruses of clade 2.3.4.4b in Europe—Why trends of virus evolution are more difficult to predict

Fusaro,

Zecchin,

Giussani

et al. 2024

Virus Evolution

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“…Spillover of H5N1 HPAI clade 2.3.4.4b viruses to mammals and their sustained transmission between mammals has been reported 13, 52 . The majority of mammals infected by the HPAI H5N1 clade 2.3.4.4b virus are carnivores, and the consumption of infected dead wild birds is presumably the basis for these spillover events 53 . In contrast to the HPAI H5N1 clade 2.3.4.4b virus infections in wild avians and wild mammals, outbreaks in farmed avian and mammal species pose a much greater risk to humans, due to its close proximity to occupational workers and -in the case of mammalian species - the favorable environment for the acquisition of mammalian-like adaptations.…”

Section: Discussionmentioning

confidence: 99%

Pigs are highly susceptible to but do not transmit mink-derived highly pathogenic avian influenza virus H5N1 clade 2.3.4.4b

Kwon,

Trujillo,

Carossino

et al. 2023

Preprint

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Rapid evolution of highly pathogenic avian influenza viruses (HPAIVs) is driven by antigenic drift but also by reassortment, which might result in robust replication in and transmission to mammals. Recently, spillover of clade 2.3.4.4b HPAIV to mammals including humans, and their transmission between mammal species has been reported. This study aimed to evaluate the pathogenicity and transmissibility of a mink-derived clade 2.3.4.4b H5N1 HPAIV isolate from Spain in pigs. Experimental infection caused moderate to severe interstitial pneumonia with necrotizing bronchiolitis with high titers of virus present in the lower respiratory tract of principal-infected pigs and 100% seroconversion. Principal-infected pigs shed limited amount of virus through the nasal and oral cavities, and importantly, there was no transmission to contact sentinel pigs. Notably, critical mammalian-like mutations such as PB2-E627K and HA-Q222L emerged at low frequencies in clinical samples and tissues derived from principal-infected pigs. It is concluded that pigs are highly susceptible to infection with the mink-derived clade 2.3.4.4b H5N1 HPAIV and provide a favorable environment for HPAI viruses to acquire mammalian-like adaptations. This work is critical for further risk assessment on the ability of the newly emerging H5N1 clade 2.3.4.4b HPAIVs to cross the species barriers into mammals.

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“…Assessment of the risk of infection with A(H5N1) clade 2.3.4.4b to humans ECDC assesses the risk of human infection with A(H5N1) clade 2.3.4.4b viruses currently circulating in Europe as low for the general public and low-to-moderate for those occupationally or otherwise exposed to animals infected with AI (ECDC, 2023b;EFSA, ECDC, EURL, 2023a.…”

Section: Immunological Situation In Humansmentioning

confidence: 99%

“…Genotypes capable of infecting new species of wild birds have thus emerged, with an inevitable impact on the temporal and spatial distribution of the virus (e.g. BB genotype infecting seabirds and causing spillover in kept mammals; EFSA, ECDC, EURL, 2023b ). Although the ability of clade 2.3.4.4b H5N1 viruses to reassort with human influenza viruses has yet to be ascertained, the potential of reassortment of previously circulating Gs/GD A(H5N1) viruses and A(H3N2) or A(H1N1) human viruses has been demonstrated through in vitro and in vivo studies (Jackson et al., 2009 ).…”

Section: Drivers Of the Currently Circulating Influenza A Viruses Tha...mentioning

confidence: 99%

“…Multiple clades of the Gs/GD lineage have caused five intercontinental epidemic waves by infecting wild birds and using their migratory routes: in 2005 clade 2.2; in 2008–2010 clade 2.3.2.1; in 2014–2015 clades 2.3.4.4c and 2.3.2.1; in 2016–2017 clade 2.3.4.4b; in 2020–2023 clade 2.3.4.4b. However, only clade 2.3.4.4b has become endemic in the wild bird populations of multiple regions including Europe and the Americas and has spread to all the continents, apart from Oceania (EFSA, ECDC, EURL, 2023b ).…”

Section: Introductionmentioning

confidence: 99%

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Drivers for a pandemic due to avian influenza and options for One Health mitigation measures

Melidou,

Enkirch,

Willgert

et al. 2024

EFS2

Self Cite

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Avian influenza viruses (AIV) remain prevalent among wild bird populations in the European Union and European Economic Area (EU/EEA), leading to significant illness and mortality of birds. Transmission between bird and mammal species has been observed, particularly in fur animal farms, where outbreaks have been reported. While transmission from infected birds to humans is rare, there have been instances of exposure to these viruses since 2020 without any symptomatic infections reported in the EU/EEA. However, these viruses continue to evolve globally, and with the migration of wild birds, new strains carrying potential mutations for mammalian adaptation could be selected. If avian A(H5N1) influenza viruses acquire the ability to spread efficiently among humans, large-scale transmission could occur due to the lack of immune defences against H5 viruses in humans. The emergence of AIV capable of infecting mammals, including humans, can be facilitated by various drivers. Some intrinsic drivers are related to virus characteristics or host susceptibility. Other drivers are extrinsic and may increase exposure of mammals and humans to AIV thereby stimulating mutation and adaptation to mammals. Extrinsic drivers include the ecology of domestic and wild host species, human activities like farming practices and the use of natural resources, climatic and environmental factors. One Health measures to mitigate the risk of AIV adapting to mammals and humans focus on limiting exposure and preventing spread. Key options for actions include enhancing surveillance targeting humans and animals, ensuring access to rapid diagnostics, promoting collaboration between animal and human sectors, and considering the implementation of preventive measures such as vaccination of poultry. Effective communication to different target audiences should be emphasised, as well as strengthening veterinary infrastructure, enforcing biosecurity measures at farms, and reducing wildlife contact with domestic animals. Careful planning of poultry and fur animal farming, especially in areas with high waterfowl density, is essential for effective risk reduction.

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Avian influenza overview April – June 2023

Cited by 26 publications

References 46 publications

High pathogenic avian influenza A(H5) viruses of clade 2.3.4.4b in Europe—Why trends of virus evolution are more difficult to predict

High pathogenic avian influenza A(H5) viruses of clade 2.3.4.4b in Europe—Why trends of virus evolution are more difficult to predict

Pigs are highly susceptible to but do not transmit mink-derived highly pathogenic avian influenza virus H5N1 clade 2.3.4.4b

Drivers for a pandemic due to avian influenza and options for One Health mitigation measures

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