Highly Pathogenic Avian Influenza H5N8 Clade 2.3.4.4b in Germany in 2016/2017

Phylodynamics of high pathogenicity avian influenza virus in Bangladesh identifying domestic ducks as the amplifying host reservoir

High pathogenicity avian influenza (HPAI) virus H5N1 first emerged in Bangladesh in 2007. Despite the use of vaccines in chickens since 2012 to control HPAI, HPAI H5Nx viruses have continued to infect poultry, and wild birds, resulting in notable mass mortalities in house crows (Corvus splendens). The first HPAI H5Nx viruses in Bangladesh belonged to clade 2.2.2, followed by clade 2.3.4.2 and 2.3.2.1 viruses in 2011. After the implementation of chicken vaccination in 2012, these viruses were mostly replaced by clade 2.3.2.1a viruses and more recently clade 2.3.4.4b and h viruses. In this study, we reconstruct the phylogenetic history of HPAI H5Nx viruses in Bangladesh to evaluate the role of major host species in the maintenance and evolution of HPAI H5Nx virus in Bangladesh and reveal the role of heavily impacted crows in virus epidemiology. Epizootic waves caused by HPAI H5N1 and H5N6 viruses amongst house crows occurred annually in winter. Bayesian phylodynamic analysis of clade 2.3.2.1a revealed frequent bidirectional viral transitions between domestic ducks, chickens, and house crows that was markedly skewed towards ducks; domestic ducks might be the source, or reservoir, of HPAI H5Nx in Bangladesh, as the number of viral transitions from ducks to chickens and house crows was by far more numerous than the other transitions. Our results suggest viral circulation in domestic birds despite vaccination, with crow epizootics acting as a sentinel. The vaccination strategy needs to be updated to use more effective vaccinations, assess vaccine efficacy, and extension of vaccination to domestic ducks, the key reservoir.

Highly Pathogenic Avian Influenza (HPAI) H5 Clade 2.3.4.4b Virus Infection in Birds and Mammals

Avian influenza viruses (AIVs) are highly contagious respiratory viruses of birds, leading to significant morbidity and mortality globally and causing substantial economic losses to the poultry industry and agriculture. Since their first isolation in 2013-2014, the Asian-origin H5 highly pathogenic avian influenza viruses (HPAI) of clade 2.3.4.4b have undergone unprecedented evolution and reassortment of internal gene segments. In just a few years, it supplanted other AIV clades, and now it is widespread in the wild migratory waterfowl, spreading to Asia, Europe, Africa, and the Americas. Wild waterfowl, the natural reservoir of LPAIVs and generally more resistant to the disease, also manifested high morbidity and mortality with HPAIV clade 2.3.4.4b. This clade also caused overt clinical signs and mass mortality in a variety of avian and mammalian species never reported before, such as raptors, seabirds, sealions, foxes, and others. Most notably, the recent outbreaks in dairy cattle were associated with the emergence of a few critical mutations related to mammalian adaptation, raising concerns about the possibility of jumping species and acquisition of sustained human-to-human transmission. The main clinical signs and anatomopathological findings associated with clade 2.3.4.4b virus infection in birds and non-human mammals are hereby summarized.

New Patterns for Highly Pathogenic Avian Influenza and Adjustment of Prevention, Control and Surveillance Strategies: The Example of France

From 2020 up to summer 2023, there was a substantial change in the situation concerning the high pathogenic avian influenza (HPAI) virus in Europe. This change concerned mainly virus circulation within wildlife, both in wild birds and wild mammals. It involved the seasonality of HPAI detections, the species affected, excess mortality events, and the apparent increased level of contamination in wild birds. The knock-on effect concerned new impacts and challenges for the poultry sector, which is affected by repeated annual waves of HPAI arriving with wild migratory birds and by risks due to viral circulation within resident wild birds across the year. Indeed, exceeding expectations, new poultry sectors and production areas have been affected during the recent HPAI seasons in France. The HPAI virus strains involved also generate considerable concern about human health because of enhanced risks of species barrier crossing. In this article, we present these changes in detail, along with the required adjustment of prevention, control, and surveillance strategies, focusing specifically on the situation in France.

Highly pathogenic avian influenza (H5N1) infection in crows through ingestion of infected crow carcasses

The present study was aimed to investigate the role of cannibalism in transmission of H5N1 avian influenza virus to house crows (Corvus splendens). Four crows were intranasally inoculated with 108.0 EID50 (A/crow/India/01CA249/2021) H5N1 highly pathogenic avian influenza (HPAI) virus and were observed for 14 days for any overt signs of illness. Two of the infected crows showed signs of wing paralysis, incoordination, and torticollis. For cannibalism experiment, two crows showing clinical signs were euthanized on 14th day post-infection (dpi) and were kept in the isolator and four naïve healthy crows were introduced along with the euthanized crows. The viscera from the infected carcasses were eaten by all the four crows. Oropharyngeal and cloacal swabs were collected up to 14 days to assess virus excretion. All four crows showed clinical signs viz., dullness, reluctance to move with ruffled feathers on 6th day post cannibalism along with neurological signs including incoordination and paralysis of the wings. All the crows gradually recovered after showing clinical signs and were euthanized on 21st day of observation period. Virus excretion was observed from 3rd to 11th day post cannibalism through both oropharyngeal and cloacal routes with maximum shedding through oropharyngeal route. The virus was isolated from lungs and trachea of one the infected crows at 21st day after euthanasia. All the four crows seroconverted against H5N1 virus infection at 14th day post cannibalism. Our study confirms the transmission of H5N1 virus in crows through cannibalism and highlights how H5N1 virus might circulate in a crow colony once they become infected.

Scavengers as Prospective Sentinels of Viral Diversity: the Snowy Sheathbill Virome as a Potential Tool for Monitoring Virus Circulation, Lessons from Two Antarctic Expeditions

Antarctica is a unique environment due to its extreme meteorological and geological conditions. In addition to this, its relative isolation from human influences has kept it undisturbed. This renders our limited understanding of its fauna and its associated microbial and viral communities a relevant knowledge gap to fill. This includes members of the order Charadriiformes such as snowy sheathbills. They are opportunistic predator/scavenger birds distributed on Antarctic and sub-Antarctic islands that are in frequent contact with other bird and mammal species. This makes them an interesting species for surveillance studies due to their high potential for the acquisition and transport of viruses. In this study, we performed whole-virome and targeted viral surveillance for coronaviruses, paramyxoviruses, and influenza viruses in snowy sheathbills from two locations, the Antarctic Peninsula and South Shetland. Our results suggest the potential role of this species as a sentinel for this region. We highlight the discovery of two human viruses, a member of the genus Sapovirus GII and a gammaherpesvirus, and a virus previously described in marine mammals. Here, we provide insight into a complex ecological picture. These data highlight the surveillance opportunities provided by Antarctic scavenger birds. IMPORTANCE This article describes whole-virome and targeted viral surveillance for coronaviruses, paramyxoviruses, and influenza viruses in snowy sheathbills from the Antarctic Peninsula and South Shetland. Our results suggest an important role of this species as a sentinel for this region. This species' RNA virome showcased a diversity of viruses likely tied to its interactions with assorted Antarctic fauna. We highlight the discovery of two viruses of likely human origin, one with an intestinal impact and another with oncogenic potential. Analysis of this data set detected a variety of viruses tied to various sources (from crustaceans to nonhuman mammals), depicting a complex viral landscape for this scavenger species.

Treatment with Toll-like Receptor (TLR) Ligands 3 and 21 Prevents Fecal Contact Transmission of Low Pathogenic H9N2 Avian Influenza Virus (AIV) in Chickens

Transmission of H9N2 avian influenza virus (AIV) can occur in poultry by direct or indirect contact with infected individuals, aerosols, large droplets and fomites. The current study investigated the potential of H9N2 AIV transmission in chickens via a fecal route. Transmission was monitored by exposing naïve chickens to fecal material from H9N2 AIV-infected chickens (model A) and experimentally spiked feces (model B). The control chickens received H9N2 AIV. Results revealed that H9N2 AIV could persist in feces for up to 60-84 h post-exposure (PE). The H9N2 AIV titers in feces were higher at a basic to neutral pH. A higher virus shedding was observed in the exposed chickens of model B compared to model A. We further addressed the efficacy of Toll-like receptor (TLR) ligands to limit transmission in the fecal model. Administration of CpG ODN 2007 or poly(I:C) alone or in combination led to an overall decrease in the virus shedding, with enhanced expression of type I and II interferons (IFNs) and interferon-stimulating genes (ISGs) in different segments of the small intestine. Overall, the study highlighted that the H9N2 AIV can survive in feces and transmit to healthy naïve chickens. Moreover, TLR ligands could be applied to transmission studies to enhance antiviral immunity and reduce H9N2 AIV shedding.

Most recent composition of the ornithofauna of the Middle Irtysh region, Russia

Aim. The work was to compile a list of bird species and their status in the forest-steppe and steppe of the Middle Irtysh region at the present time and to analyse their potential ability in terms of the transmission of influenza viruses that pose a danger to humans and farm animals.

Materials and Methods. The study of avifauna and their status in the forest-steppe and steppe of the Middle Irtysh region has been conducted by us from 1973 to the present. The analysis of literary sources has been carried out since the time of P.S. Pallas's travels in the region in 1871. In addition, information on the wetlands of the Irtysh region which is freely available on the Internet was used.

Results. At the beginning of the 20th century, about 200 species of birds were recorded in the vicinity of Omsk, 125 of them being breeding species. At present about 150 species of birds have been recorded in Omsk and its environs. Of the 290 bird species of the Middle Irtysh region, 48 species (16.6%) belong among the natural hosts of influenza A viruses. Of these, at least 40 species are migratory and 25 species nest there. In addition to the prinicipal influenza virus host species, the list of birds of the Middle Irtysh region includes several species of scavengers and predators, as well as synanthropic bird species. These species may share habitat or food resources with the main host species of influenza viruses. Influenza A viruses can be transmitted between species either by direct or indirect contact through mechanical propagation or contamination of nutritional resources.

Conclusion. As the 3 largest bird migratory flyways run through the Middle Irtysh region where there is a significant number of wetlands, the prerequisites are created for a mass simultaneous accumulation of different populations and species of migratory birds carrying viruses and, accordingly, a high probability of exchanging viral genomes with each other and their further spread to new regions.

Experimental and natural infections of white-tailed sea eagles (Haliaeetus albicilla) with high pathogenicity avian influenza virus of H5 subtype

White-tailed sea eagle (Haliaeetus albicilla), a regionally rare species of raptor, is threatened in several countries. To assess the risk of H5 high pathogenicity avian influenza (HPAI) viral infection in rare bird species, we performed experimental infections with a GS/GD96-lineage H5N6 HPAI virus of clade 2.3.4.4e in white-tailed sea eagles. Additionally, during the winter of 2020–2021 in Japan, we accidentally encountered a white-tailed sea eagle that had a fatal outcome due to natural infection with a GS/GD96-lineage H5N8 HPAI virus of clade 2.3.4.4b, allowing us to compare experimental and natural infections in the same rare raptor species. Our experiments demonstrated the susceptibility of white-tailed sea eagles to the GS/GD96-lineage H5 HPAI virus with efficient replication in systemic organs. The potential for the viruses to spread within the white-tailed sea eagle population through indirect transmission was also confirmed. Comprehensive comparisons of both viral distribution and histopathological observations between experimentally and naturally infected white-tailed sea eagles imply that viral replication in the brain is responsible for the disease severity and mortality in this species. These findings provide novel insights into the risk assessment of H5 HPAI viral infection in white-tailed sea eagles, proper diagnostic procedures, potential risks to artificially fed eagle populations and persons handling superficially healthy eagles, potential impact of intragastric infection on eagle outcomes, and possibility of severity of the disease being attributed to viral replication in the brain.

Disentangling the role of poultry farms and wild birds in the spread of highly pathogenic avian influenza virus in Europe

In winter 2016-7, Europe was severely hit by an unprecedented epidemic of highly pathogenic avian influenza viruses (HPAIVs), causing a significant impact on animal health, wildlife conservation, and livestock economic sustainability. By applying phylodynamic tools to virus sequences collected during the epidemic, we investigated when the first infections occurred, how many infections were unreported, which factors influenced virus spread, and how many spillover events occurred. HPAIV was likely introduced into poultry farms during the autumn, in line with the timing of wild birds' migration. In Germany, Hungary, and Poland, the epidemic was dominated by farm-to-farm transmission, showing that understanding of how farms are connected would greatly help control efforts. In the Czech Republic, the epidemic was dominated by wild bird-to-farm transmission, implying that more sustainable prevention strategies should be developed to reduce HPAIV exposure from wild birds. Inferred transmission parameters will be useful to parameterize predictive models of HPAIV spread. None of the predictors related to live poultry trade, poultry census, and geographic proximity were identified as supportive predictors of HPAIV spread between farms across borders. These results are crucial to better understand HPAIV transmission dynamics at the domestic-wildlife interface with the view to reduce the impact of future epidemics.

Molecular Epidemiology and Evolutionary Analysis of Avian Influenza A(H5) Viruses Circulating in Egypt, 2019–2021

The highly pathogenic avian influenza (HPAI) H5N8 virus was first detected in Egypt in late 2016. Since then, the virus has spread rapidly among different poultry sectors, becoming the dominant HPAI H5 subtype reported in Egypt. Different genotypes of the HPAI H5N8 virus were reported in Egypt; however, the geographic patterns and molecular evolution of the Egyptian HPAI H5N8 viruses are still unclear. Here, extensive epidemiological surveillance was conducted, including more than half a million samples collected from different poultry sectors (farms/backyards/live bird markets) from all governorates in Egypt during 2019–2021. In addition, genetic characterization and evolutionary analyses were performed using 47 selected positive H5N8 isolates obtained during the same period. The result of the conducted surveillance showed that HPAI H5N8 viruses of clade 2.3.4.4b continue to circulate in different locations in Egypt, with an obvious seasonal pattern, and no further detection of the HPAI H5N1 virus of clade 2.2.1.2 was observed in the poultry population during 2019–2021. In addition, phylogenetic and Bayesian analyses revealed that two major genotypes (G5 and G6) of HPAI H5N8 viruses were continually expanding among the poultry sectors in Egypt. Notably, molecular dating analysis suggested that the Egyptian HPAI H5N8 virus is the potential ancestral viruses of the European H5N8 viruses of 2020–2021. In summary, the data of this study highlight the current epidemiology, diversity, and evolution of HPAI H5N8 viruses in Egypt and call for continuous monitoring of the genetic features of the avian influenza viruses in Egypt.

Highly Pathogenic Avian Influenza (HPAI H5Nx, Clade 2.3.4.4.b) in Poultry and Wild Birds in Sweden: Synopsis of the 2020-2021 Season

Highly pathogenic avian influenza (HPAI, Gs/Gd lineage) was introduced to Europe in 2005 and has since caused numerous outbreaks in birds. The 2020-2021 season was the hitherto most devastating when considering bird numbers and duration in Europe. Surveillance data, virologic results and epidemiologic investigations from the 2020-2021 outbreaks in Sweden were analysed. Subtypes H5N8 and H5N5 were detected on 24 farms with poultry or other captive birds. In wild birds, subtypes H5N8, H5N5, H5N1, H5N4, H5Nx were detected in 130 out of 811 sampled birds. There was a spatiotemporal association between cases in wild birds and poultry. Based on phylogeny and epidemiology, most of the introductions of HPAI to commercial poultry were likely a result of indirect contact with wild birds. A definite route of introduction to poultry could not be established although some biosecurity breaches were observed. No spread between farms was identified but airborne spread between flocks on the same farm was suspected. Our findings exemplify the challenges posed by the continuously changing influenza viruses that seem to adapt to a broader species spectrum. This points to the importance of wild bird surveillance, compliance to biosecurity, and identification of risk factors for introduction on poultry farms.

Highly pathogenic avian influenza virus of the A/H5N8 subtype, clade 2.3.4.4b, caused outbreaks in Kazakhstan in 2020

Background

Large poultry die-offs happened in Kazakhstan during autumn of 2020. The birds' disease appeared to be avian influenza. Northern Kazakhstan was hit first and then the disease propagated across the country affecting eleven provinces. This study reports the results of full-genome sequencing of viruses collected during the outbreaks and investigation of their relationship to avian influenza virus isolates in the contemporary circulation in Eurasia.

Methods

Samples were collected from diseased birds during the 2020 outbreaks in Kazakhstan. Initial virus detection and subtyping was done using RT-PCR. Ten samples collected during expeditions to Northern and Southern Kazakhstan were used for full-genome sequencing of avian influenza viruses. Phylogenetic analysis was used to compare viruses from Kazakhstan to viral isolates from other world regions.

Results

Phylogenetic trees for hemagglutinin and neuraminidase show that viruses from Kazakhstan belong to the A/H5N8 subtype and to the hemagglutinin H5 clade 2.3.4.4b. Deduced hemagglutinin amino acid sequences in all Kazakhstan's viruses in this study contain the polybasic cleavage site (KRRKR-G) indicative of the highly pathogenic phenotype. Building phylogenetic trees with the Bayesian phylogenetics results in higher statistical support for clusters than using distance methods. The Kazakhstan's viruses cluster with isolates from Southern Russia, the Russian Caucasus, the Ural region, and southwestern Siberia. Other closely related prototypes are from Eastern Europe. The Central Asia Migratory Flyway passes over Kazakhstan and birds have intermediate stops in Northern Kazakhstan. It is postulated that the A/H5N8 subtype was introduced with migrating birds.

Conclusion

The findings confirm the introduction of the highly pathogenic avian influenza viruses of the A/Goose/Guangdong/96 (Gs/GD) H5 lineage in Kazakhstan. This virus poses a tangible threat to public health. Considering the results of this study, it looks justifiable to undertake measures in preparation, such as install sentinel surveillance for human cases of avian influenza in the largest pulmonary units, develop a human A/H5N8 vaccine and human diagnostics capable of HPAI discrimination.

Surveillance of Highly Pathogenic Avian Influenza Viruses (H5Nx Subtypes) in Wild Birds in Iran, 2014-2019

After the emergence of the highly pathogenic avian influenza viruses (HPAIV) subtypes H5N6 in 2013 and H5N8 in 2014, a surveillance study using molecular epidemiology approaches was carried out during 2014 - 2019 in Iran to discover any potential introduction or outbreak of HPAIV in wild bird populations. All sick and dead wild birds found in nature, or in cases of an outbreak, a collection of representative samples was tested using the specific molecular methods for HPAIV H5 subtypes. Additionally, wild bird species in wetlands, several zoos, zoological gardens, or rehabilitation centers were tested for HPAIV. During the active surveillance plan, several individual and outbreak cases of HPAIV and orthoavulaviruses were identified. In general, more than 900 fecal materials, cloacal and oropharyngeal swabs, and/or tissue samples were collected from apparently healthy live birds representing several different species and families. In addition, tissue and swab samples were collected and investigated from any reported wild birds' mortality cases in different parts of Iran in the framework of this study. No positive bird was found among apparently healthy live birds; however, the highly pathogenic influenza viruses of H5N1, H5N2, H5N6, and H5N8 were found in individual dead birds or mass die-off cases.

Avian influenza A virus susceptibility, infection, transmission, and antibody kinetics in European starlings

Avian influenza A viruses (IAVs) pose risks to public, agricultural, and wildlife health. Bridge hosts are spillover hosts that share habitat with both maintenance hosts (e.g., mallards) and target hosts (e.g., poultry). We conducted a comprehensive assessment of European starlings (Sturnus vulgaris), a common visitor to both urban and agricultural environments, to assess whether this species might act as a potential maintenance or bridge host for IAVs. First, we experimentally inoculated starlings with a wild bird IAV to investigate susceptibility and replication kinetics. Next, we evaluated whether IAV might spill over to starlings from sharing resources with a widespread IAV reservoir host. We accomplished this using a specially designed transmission cage to simulate natural environmental transmission by exposing starlings to water shared with IAV-infected mallards (Anas platyrhynchos). We then conducted a contact study to assess intraspecies transmission between starlings. In the initial experimental infection study, all inoculated starlings shed viral RNA and seroconverted. All starlings in the transmission study became infected and shed RNA at similar levels. All but one of these birds seroconverted, but detectable antibodies were relatively transient, falling to negative levels in a majority of birds by 59 days post contact. None of the contact starlings in the intraspecies transmission experiment became infected. In summary, we demonstrated that starlings may have the potential to act as IAV bridge hosts if they share water with IAV-infected waterfowl. However, starlings are unlikely to act as maintenance hosts due to limited, if any, intraspecies transmission. In addition, starlings have a relatively brief antibody response which should be considered when interpreting serology from field samples. Further study is needed to evaluate the potential for transmission from starlings to poultry, a possibility enhanced by starling's behavioral trait of forming very large flocks which can descend on poultry facilities when natural resources are scarce.

Molecular Characterization of Highly Pathogenic Avian Influenza Viruses H5N6 Detected in Denmark in 2018-2019

Beginning in late 2017, highly pathogenic avian influenza (HPAI) H5N6 viruses caused outbreaks in wild birds and poultry in several European countries. H5N6 viruses were detected in 43 wild birds found dead throughout Denmark. Most of the Danish virus-positive dead birds were found in the period from February to April 2018. However, unlike the rest of Europe, sporadic HPAI H5N6-positive dead wild birds were detected in Denmark in July, August, September, and December 2018, with the last positive bird being found in January 2019. HPAI viruses were not detected in active surveillance of apparently healthy wild birds. In this study, we use full genome sequencing and phylogenetic analysis to investigate the wild bird HPAI H5N6 viruses found in Denmark. The Danish viruses were found to be closely related to those of contemporary HPAI H5N6 viruses detected in Europe. Their sequences formed two clusters indicating that at least two or more introductions of H5N6 into Denmark occurred. Notably, all viruses detected in the latter half of 2018 and in 2019 grouped into the same cluster. The H5N6 viruses appeared to have been maintained undetected in the autumn 2018.

Exposure of wild boar to Influenza A viruses in Bavaria: Analysis of seroprevalences and antibody subtype specificity before and after the panzootic of highly pathogenic avian influenza viruses A (H5N8)

Swine influenza A viruses (S-IAV) circulate in wild boar populations worldwide. Subtypes primarily reflect those actually present within the respective pig industry. Accordingly, infections with swine H1N1, H1N2 and H3N2 have been reported for several regions of Germany. As pigs are susceptible not only to S-IAV but also to avian and human influenza A viruses, it is necessary to consider the possibility that new reassortant viruses with pandemic potential may arise in these new hosts. Therefore, in this study the impact of recent IAV epidemics on antibody prevalences in Bavarian wild boar was assessed. Important events considered were the H1N1pdm09 pandemic, which affected humans and swine, and the highly pathogenic avian influenza (HPAI) H5N8 panzootic in 2016 and 2017, affecting wild and domestic birds. IAV seroprevalences were determined analysing 1,396 samples from before and after the H5N8 panzootic, from various regions in Bavaria, a large administrative region in the South of Germany. Taken together, seroprevalences varied markedly from 1.44% to 12.59%, relative to region and time. However, no discrete correlation was found to population density either in wild boar or in pigs. Antibodies against H1N1 were the most prevalent. In addition, antibodies were detected reacting against H1N2 and against H1pdmNx reassortant viruses, already known to circulate in domestic pigs in Bavaria and notably also against the avian influenza A virus H5N8; the latter in samples taken in 2017. These results confirm the exposure of wild boar to IAV of diverse origin and the increasing variability of S-IAV present in the field. The necessity for continuous IAV surveillance not only of domestic swine but also of wildlife is emphasized.

Management and biosecurity practices by small to medium egg producers in Scotland

1. Information about procedures and biosecurity practices used by small and medium egg producers (SMEPs) is scarce. Anecdotal evidence suggests that biosecurity in such enterprises may be poor, as personnel and equipment move freely between sites and this may be compounded by personnel working on commercial units who keep their own poultry.2. To fill this knowledge gap, a questionnaire was designed and implemented targeting SMEPs in Scotland. Small enterprises were defined as egg producers that have ≥50 laying hens but <350 laying hens; while medium enterprises were defined as egg producers that have ≥350 laying hens but ≤32 000 laying hens. The questionnaire consisted of a total of 56 questions divided into multiple sections, covering the characteristics of the primary keeper, location of the enterprise and size of the flocks, husbandry, marketing of products and health/biosecurity.3. The questionnaire was posted to 375 holdings at the beginning of March 2017 and the survey remained open until the end of May 2017. In total 90 questionnaires were received by the cut-off date of which 76 questionnaires were from SMEPs. Forty were small enterprises and 36 were medium enterprises. For three questionnaires, it was not possible to identify the enterprise type.4. Differences were observed between SMEPs in terms of reported biosecurity and management practices, with medium enterprises reporting the adoption of more biosecurity measures than small enterprises. Furthermore, SMEPs behave differently from backyard poultry keepers and large commercial companies in terms of disease risk.5. In conclusion, it is important to ensure that SMEPs are considered in contingency plans and disease control programmes and that engagement with them is promoted so that the uptake of relevant information, such as awareness of disease control programmes, is optimised.

Highly Pathogenic Avian Influenza Viruses at the Wild-Domestic Bird Interface in Europe: Future Directions for Research and Surveillance

Highly pathogenic avian influenza (HPAI) outbreaks in wild birds and poultry are no longer a rare phenomenon in Europe. In the past 15 years, HPAI outbreaks—in particular those caused by H5 viruses derived from the A/Goose/Guangdong/1/1996 lineage that emerged in southeast Asia in 1996—have been occuring with increasing frequency in Europe. Between 2005 and 2020, at least ten HPAI H5 incursions were identified in Europe resulting in mass mortalities among poultry and wild birds. Until 2009, the HPAI H5 virus outbreaks in Europe were caused by HPAI H5N1 clade 2.2 viruses, while from 2014 onwards HPAI H5 clade 2.3.4.4 viruses dominated outbreaks, with abundant genetic reassortments yielding subtypes H5N1, H5N2, H5N3, H5N4, H5N5, H5N6 and H5N8. The majority of HPAI H5 virus detections in wild and domestic birds within Europe coincide with southwest/westward fall migration and large local waterbird aggregations during wintering. In this review we provide an overview of HPAI H5 virus epidemiology, ecology and evolution at the interface between poultry and wild birds based on 15 years of avian influenza virus surveillance in Europe, and assess future directions for HPAI virus research and surveillance, including the integration of whole genome sequencing, host identification and avian ecology into risk-based surveillance and analyses.

Genetic characterization of highly pathogenic avian Influenza H5Nx clade 2.3.4.4b reveals independent introductions in nigeria

Among recurrent sanitary emergencies able to spread rapidly worldwide, avian influenza is one of the main constraints for animal health and food security. In West Africa, Nigeria has been experiencing repeated outbreaks of different strains of avian influenza virus (AIV) since 2006 and is also recognized as a hot spot in the region for the introduction of emerging strains by migratory wild birds. Here, we generated complete genomes of 20 highly pathogenic avian influenza (HPAI) H5N8 viruses collected during active surveillance in Nigerian live bird markets (LBM) and from outbreaks reported in the country between 2016 and 2019. Phylogenetic analysis reveals that the Nigerian viruses cluster into four separate genetic groups within HPAI H5 clade 2.3.4.4b. The first group includes 2016-2017 Nigerian viruses with high genetic similarity to H5N8 viruses detected in Central African countries, while the second includes Nigerian viruses collected both in LBM and poultry farms (2018-2019), as well as in Cameroon, Egypt and Siberia. A natural reassortant strain identified in 2019 represents the third group: H5N8 viruses with the same gene constellation were identified in 2018 in South Africa. Finally, the fourth introduction represents the first detection in the African continent of the H5N6 subtype, which is related to European viruses. Bayesian phylogeographic analyses confirmed that the four introductions originated from different sources and provide evidence of the virus spread within Nigeria, as well as diffusion beyond its borders. The multiple epidemiological links between Nigeria, Central and Southern African countries highlight the need for harmonized and coordinated surveillance system to control AIV impact. Improved surveillance at the Wetlands, LBMs and early warning of outbreaks are crucial for prevention and control of AIV, which can be potentially zoonotic and be a threat to human health.

Spatiotemporal reconstruction and transmission dynamics during the 2016-17 H5N8 highly pathogenic avian influenza epidemic in Italy

Effective control of avian diseases in domestic populations requires understanding of the transmission dynamics facilitating viral emergence and spread. In 2016-17, Italy experienced a significant avian influenza epidemic caused by a highly pathogenic A(H5N8) virus, which affected domestic premises housing around 2.7 million birds, primarily in the north-eastern regions with the highest density of poultry farms (Lombardy, Emilia-Romagna and Veneto). We perform integrated analyses of genetic, spatiotemporal and host data within a Bayesian phylogenetic framework. Using continuous and discrete phylogeography, we estimate the locations of movements responsible for the spread and persistence of the epidemic. The information derived from these analyses on rates of transmission between regions through time can be used to assess the success of control measures. Using an approach based on phylogenetic-temporal distances between domestic cases, we infer the presence of cryptic wild bird-mediated transmission, information that can be used to complement existing epidemiological methods for distinguishing transmission within the domestic population from incursions across the wildlife-domestic interface, a common challenge in veterinary epidemiology. Spatiotemporal reconstruction of the epidemic reveals a highly skewed distribution of virus movements with a high proportion of shorter distance local movements interspersed with occasional long-distance dispersal events associated with wild birds. We also show how such inference be used to identify possible instances of human-mediated movements where distances between phylogenetically linked domestic cases are unusually high.

Experimental infection of domestic geese (Anser anser var. domesticus) with H5N8 Gs/GD and H7N1 highly pathogenic avian influenza viruses

Prior to the emergence of the Asian-origin H5 Goose/Guangdong/1/96 (Gs/GD) lineage, highly pathogenic avian influenza viruses (HPAIV) had rarely caused high mortalities in domestic geese. In 2016/2017 European epidemics, H5N8 Gs/GD clade 2.3.4.4 Group B produced an unprecedented number of outbreaks in waterfowl holdings. In this study, the pathogenesis of H5N8 HPAIV in comparison with H7N1 HPAIV, and the role of domestic geese in the epidemiology of these viruses, were evaluated. Local and commercial geese (Anser anser var. domesticus) were intranasally inoculated with 10⁵ ELD₅₀ of A/goose/Spain/IA17CR02699/2017 (H5N8) or A/Chicken/Italy/5093/1999 (H7N1) and monitored daily during 15 days. H5N8 was highly virulent to domestic geese, reaching 100% mortality by 10 days post-infection. Systemic microscopic necrotizing lesions associated with widespread AIV-antigen were detected by IHC techniques, the central nervous system being the most severely affected. High viral loads, measured by qRT-PCR, were present in all samples collected: oral and cloacal swabs, plasma tissues, and moderate levels in pool water. Domestic geese were also susceptible to H7N1 infection, as demonstrated by seroconversion and detection of viral RNA in tissues and plasma in some geese, but all lacked clinical signs. Viral shedding was confirmed in only some geese and was restricted to the oral route, but levels were high and still detected at the end of the study. Overall, H7N1 presents a lower lethality and shedding than H5N8 in geese; however, the viral shedding indicates that these species could play a role in the epidemiology of Gs/GD and other lineages of HPAIVs. RESEARCH HIGHLIGHTS H5N8 Gs/GD clade 2.3.4.4 Group B is highly virulent to domestic geese. The severity of H5N8 is associated with multisystemic replication. H7N1 can infect domestic geese but is avirulent to this species. Domestic geese could play a role in the epidemiology of Gs/GD HPAIVs.

A Review of Avian Influenza A Virus Associations in Synanthropic Birds

Avian influenza A viruses (IAV) have received significant attention due to the threat they pose to human, livestock, and wildlife health. In this review, we focus on what is known about IAV dynamics in less common avian species that may play a role in trafficking IAVs to poultry operations. Specifically, we focus on synanthropic bird species. Synanthropic species, otherwise known as peridomestic, are species that are ecologically associated with humans and anthropogenically modified landscapes, such as agricultural and urban areas. Aquatic birds such as waterfowl and shorebirds are the species most commonly associated with avian IAVs, and are generally considered the reservoir or maintenance hosts in the natural ecology of these viruses. Waterfowl and shorebirds are occasionally associated with poultry facilities, but are uncommon or absent in many areas, especially large commercial operations. In these cases, spillover hosts that share resources with both maintenance hosts and target hosts such as poultry may play an important role in introducing wild bird viruses onto farms. Consequently, our focus here is on what is known about IAV dynamics in synanthropic hosts that are commonly found on both farms and in nearby habitats, such as fields, lakes, wetlands, or riparian areas occupied by waterfowl or shorebirds.

The genetics of highly pathogenic avian influenza viruses of subtype H5 in Germany, 2006-2020

The H5 A/Goose/Guangdong/1/1996 (gs/GD) lineage emerged in China in 1996. Rooted in the respective gs/GD lineage, the hemagglutinin (HA) gene of highly pathogenic avian influenza viruses (HPAIV) has genetically diversified into a plethora of clades and subclades and evolved into an assortment of sub- and genotypes. Some caused substantial losses in the poultry industry and had a major impact on wild bird populations alongside public health implications due to a zoonotic potential of certain clades. After the primary introduction of the HPAI H5N1 gs/GD lineage into Europe in autumn 2005 and winter 2005/2006, Germany has seen recurring incursions of four varying H5Nx subtypes (H5N1, H5N8, H5N5, H5N6) carrying multiple distinct reassortants, all descendants of the gs/GD virus. The first HPAIV H5 epidemic in Germany during 2006/2007 was caused by a clade 2.2 subtype H5N1 virus. Phylogenetic analysis confirmed three distinct clusters belonging to clades 2.2.1, 2.2.2 and 2.2, concurring with geographic and temporal structures. From 2014 onwards, HPAIV clade 2.3.4.4 has dominated the epidemiological situation in Germany. The initial clade 2.3.4.4a HPAIV H5N8, reaching Germany in November 2014, caused a limited epidemic affecting five poultry holdings, one zoo in Northern Germany and few wild birds. After November 2016, HPAIV of clade 2.3.4.4b have dominated the situation to date. The most extensive HPAIV H5 epidemic on record reached Germany in winter 2016/2017, encompassing multiple incursion events with two subtypes (H5N8, H5N5) and entailing five reassortants. A novel H5N6 clade 2.3.4.4b strain affected Germany from December 2017 onwards, instigating low-level infection in smallholdings and wild birds. Recently, in spring 2020, a novel incursion of a genetically distinct HPAI clade 2.3.4.4b H5N8 virus caused another epidemic in Europe, which affected a small number of poultry holdings, one zoo and two wild birds throughout Germany.

Rapid multiplex MinION nanopore sequencing workflow for Influenza A viruses

BACKGROUND

Due to the frequent reassortment and zoonotic potential of influenza A viruses, rapid gain of sequence information is crucial. Alongside established next-generation sequencing protocols, the MinION sequencing device (Oxford Nanopore Technologies) has become a serious competitor for routine whole-genome sequencing. Here, we established a novel, rapid and high-throughput MinION multiplexing workflow based on a universal RT-PCR.

METHODS

Twelve representative influenza A virus samples of multiple subtypes were universally amplified in a one-step RT-PCR and subsequently sequenced on the MinION instrument in conjunction with a barcoding library preparation kit from the rapid family and the MinIT performing live base-calling. The identical PCR products were sequenced on an IonTorrent platform and, after final consensus assembly, all data was compared for validation. To prove the practicability of the MinION-MinIT method in human and veterinary diagnostics, we sequenced recent and historical influenza strains for further benchmarking.

RESULTS

The MinION-MinIT combination generated over two million reads for twelve samples in a six-hour sequencing run, from which a total of 72% classified as quality screened, trimmed and mapped influenza reads to produce full genome sequences. Identities between the datasets of > 99.9% were achieved, with 100% coverage of all segments alongside a sufficient confidence and 4492fold mean depth. From RNA extraction to finished sequences, only 14 h were required.

CONCLUSIONS

Overall, we developed and validated a novel and rapid multiplex workflow for influenza A virus sequencing. This protocol suits both clinical and academic settings, aiding in real time diagnostics and passive surveillance.

Genetic Characterization and Zoonotic Potential of Highly Pathogenic Avian Influenza Virus A(H5N6/H5N5), Germany, 2017-2018

We genetically characterized highly pathogenic avian influenza virus A(H5N6) clade 2.3.4.4b isolates found in Germany in 2017–2018 and assessed pathogenicity of representative H5N5 and H5N6 viruses in ferrets. These viruses had low pathogenicity; however, continued characterization of related isolates is warranted because of their high potential for reassortment.

A brief history of bird flu

In 1918, a strain of influenza A virus caused a human pandemic resulting in the deaths of 50 million people. A century later, with the advent of sequencing technology and corresponding phylogenetic methods, we know much more about the origins, evolution and epidemiology of influenza epidemics. Here we review the history of avian influenza viruses through the lens of their genetic makeup: from their relationship to human pandemic viruses, starting with the 1918 H1N1 strain, through to the highly pathogenic epidemics in birds and zoonoses up to 2018. We describe the genesis of novel influenza A virus strains by reassortment and evolution in wild and domestic bird populations, as well as the role of wild bird migration in their long-range spread. The emergence of highly pathogenic avian influenza viruses, and the zoonotic incursions of avian H5 and H7 viruses into humans over the last couple of decades are also described. The threat of a new avian influenza virus causing a human pandemic is still present today, although control in domestic avian populations can minimize the risk to human health.

This article is part of the theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes’. This issue is linked with the subsequent theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control’.

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

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.

Novel HPAIV H5N8 Reassortant (Clade 2.3.4.4b) Detected in Germany

A novel H5N8 highly pathogenic avian influenza virus (HPAIV) was detected in a greater white-fronted goose in January 2020 in Brandenburg, Germany, and, in February 2020, in domestic chickens belonging to a smallholding in Baden-Wuerttemberg, Germany. Full-genome sequencing was conducted on the MinION platform, enabling further phylogenetic analyses. The virus of clade 2.3.4.4b holds six segments from a Eurasian/Asian/African HPAIV H5N8 reassortant and two segments from low pathogenic avian influenza H3N8 subtype viruses recently detected in wild birds in Central Russia. These new entries continue to show the reassortment potential of the clade 2.3.4.4 H5Nx viruses, underlining the necessity for full-genome sequencing and continuous surveillance.

Pathogenicity of H5 highly pathogenic avian influenza virus in rooks (Corvus frugilegus)

Rooks (Corvus frugilegus) are considered migratory crows in Japan. Some rooks share a wintering site in the Izumi plain in Kagoshima Prefecture with hooded cranes (Grus monacha) and white-necked cranes (Grus vipio), which are designated as "endangered" in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Highly pathogenic avian influenza (HPAI), caused by H5 subtype viruses, has recently been reported in these crane species in Japan, in conjunction with a massive decrease in their population. In the present study, the pathogenicity of HPAI virus was assessed in rooks to evaluate the likelihood that they are a source of infections in other bird species. One of four rooks intranasally inoculated with A/mandarin duck/Miyazaki/22M807-1/2011 (H5N1) died at 10 days post-inoculation (d.p.i.). The other three rooks exhibited seroconversion but no clinical signs. All the rooks had shed virus by the oral route at <10³ 50% egg infectious dose/ml until 7 d.p.i. Virus was also recovered from multiple tissues of the rook that succumbed to the infection. These results suggest that rooks are susceptible to infection with H5 HPAI viruses, leading to prolonged viral shedding. The rooks shed the virus at low titres however, indicating that they are likely to function as transmission vectors in wintering bird flocks. The rooks exhibited clear antibody responses against the H5 HPAI virus, and thus serological surveillance of them in the field should be helpful for assessing viral pervasion into the habitats of crane species.

Pathogenicity and genomic changes of a 2016 European H5N8 highly pathogenic avian influenza virus (clade 2.3.4.4) in experimentally infected mallards and chickens

Highly pathogenic avian influenza H5N8 clade 2.3.4.4 virus caused outbreaks in poultry and unusually high mortality in wild birds in 2016-2017. The pathobiology of one of these viruses was examined in mallards and chickens. High mortality and transmission to direct contacts were observed in mallards inoculated with medium and high doses of the virus. However, in chickens, high mortality occurred only when birds are given the high virus dose and no transmission was observed, indicating that the virus was better adapted to mallards. In comparison with the virus inoculum, viral sequences obtained from the chickens had a higher number of nucleotide changes but lower intra-host genomic diversity than viral sequences obtained from the mallards. These observations are consistent with population bottlenecks occurring when viruses infect and replicate in a host that it is not well adapted to. Whether these observations apply to influenza viruses in general remains to be determined.

Comparative micro-epidemiology of pathogenic avian influenza virus outbreaks in a wild bird population

Understanding the epidemiological dynamics of highly pathogenic avian influenza virus (HPAIV) in wild birds is crucial for guiding effective surveillance and control measures. The spread of H5 HPAIV has been well characterized over large geographical and temporal scales. However, information about the detailed dynamics and demographics of individual outbreaks in wild birds is rare and important epidemiological parameters remain unknown. We present data from a wild population of long-lived birds (mute swans; Cygnus olor) that has experienced three outbreaks of related H5 HPAIVs in the past decade, specifically, H5N1 (2007), H5N8 (2016) and H5N6 (2017). Detailed demographic data were available and intense sampling was conducted before and after the outbreaks; hence the population is unusually suitable for exploring the natural epidemiology, evolution and ecology of HPAIV in wild birds. We show that key epidemiological features remain remarkably consistent across multiple outbreaks, including the timing of virus incursion and outbreak duration, and the presence of a strong age-structure in morbidity that likely arises from an equivalent age-structure in immunological responses. The predictability of these features across a series of outbreaks in a complex natural population is striking and contributes to our understanding of HPAIV in wild birds. This article is part of the theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes'. This issue is linked with the subsequent theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control'.

Spread of Highly Pathogenic Avian Influenza (HPAI) H5N5 Viruses in Europe in 2016-2017 Appears Related to the Timing of Reassortment Events

During the epizootic of highly pathogenic avian influenza (HPAI) H5N8 virus in Europe in 2016-2017, HPAI viruses of subtype H5N5 were also isolated. However, the detection of H5N5 viruses was limited compared to H5N8. In this study, we show that the genetic constellation of a newly isolated H5N5 virus is different from two genotypes previously identified in the Netherlands. The introduction and spread of the three H5N5 genotypes in Europe was studied using spatiotemporal and genetic analysis. This demonstrated that the genotypes were isolated in distinguishable phases of the epizootic, and suggested multiple introductions of H5N5 viruses into Europe followed by local spread. We estimated the timing of the reassortment events, which suggested that the genotypes emerged after the start of autumn migration. This may have prevented large-scale spread of the H5N5 viruses on wild bird breeding sites before introduction into Europe. Experiments in primary chicken and duck cells revealed only minor differences in cytopathogenicity and replication kinetics between H5N5 genotypes and H5N8. These results suggest that the limited spread of HPAI H5N5 viruses is related to the timing of the reassortment events rather than changes in virus pathogenicity or replication kinetics.

Integration of genetic and epidemiological data to infer H5N8 HPAI virus transmission dynamics during the 2016-2017 epidemic in Italy

Between October 2016 and December 2017, several European Countries had been involved in a massive Highly Pathogenic Avian Influenza (HPAI) epidemic sustained by H5N8 subtype virus. Starting on December 2016, also Italy was affected by H5N8 HPAI virus, with cases occurring in two epidemic waves: the first between December 2016 and May 2017, and the second in July-December 2017. Eighty-three outbreaks were recorded in poultry, 67 of which (80.72%) occurring in the second wave. A total of 14 cases were reported in wild birds. Epidemiological information and genetic analyses were conjointly used to get insight on the spread dynamics. Analyses indicated multiple introductions from wild birds to the poultry sector in the first epidemic wave, and noteworthy lateral spread from October 2017 in a limited geographical area with high poultry densities. Turkeys, layers and backyards were the mainly affected types of poultry production. Two genetic sub-groups were detected in the second wave in non-overlapping geographical areas, leading to speculate on the involvement of different wild bird populations. The integration of epidemiological data and genetic analyses allowed to unravel the transmission dynamics of H5N8 virus in Italy, and could be exploited to timely support in implementing tailored control measures.

Avian influenza overview May - August 2018

Between 16 May and 15 August 2018, three highly pathogenic avian influenza (HPAI) A(H5N8) outbreaks in poultry establishments and three HPAI A(H5N6) outbreaks in wild birds were reported in Europe. Three low pathogenic avian influenza (LPAI) outbreaks were reported in three Member States. Few HPAI and LPAI bird cases have been detected in this period of the year, in accordance with the seasonal expected pattern of LPAI and HPAI. There is no evidence to date that HPAI A(H5N8) and A(H5N6) viruses circulating in Europe have caused any human infections. The risk of zoonotic transmission to the general public in Europe is considered to be very low. Several HPAI outbreaks in poultry were reported during this period from Russia. The presence of the A(H5N2) and A(H5N8) viruses in parts of Russia connected with fall migration routes of wild birds is of concern for possible introduction and spread with wild birds migrating to the EU. Although few AI outbreaks were observed in Africa, Asia and the Middle East during the reporting period, the probability of AI virus introductions from non‐EU countries via wild birds particularly via the north‐eastern route from Russia is increasing, as the fall migration of wild birds will start in the coming weeks. Further, the lower temperatures in autumn and winter may facilitate the environmental survival of avian influenza viruses potentially introduced to Europe.

White-Tailed Sea Eagle (Haliaeetus albicilla) Die-Off Due to Infection with Highly Pathogenic Avian Influenza Virus, Subtype H5N8, in Germany

In contrast to previous incursions of highly pathogenic avian influenza (HPAIV) H5 viruses, H5N8 clade 2.3.4.4b viruses caused numerous cases of lethal infections in white-tailed sea eagles (Haliaeetus albicilla) affecting mainly young eagles (younger than five years of age) in Germany during winter 2016/2017. Until April 2017, 17 HPAIV H5N8-positive white-tailed sea eagles had been detected (three found alive and 14 carcasses) by real-time RT-PCR and partial nucleotide sequence analyses. Severe neurological clinical signs were noticed which were corroborated by immunohistopathology revealing mild to moderate, oligo- to multifocal necrotizing virus-induced polioencephalitis. Lethal lead (Pb) concentrations, a main factor of mortality in sea eagles in previous years, could be ruled out by atomic absorption spectrometry. HPAIV H5 clade 2.3.4.4b reportedly is the first highly pathogenic influenza virus known to induce fatal disease in European white-tailed see eagles. This virus strain may become a new health threat to a highly protected species across its distribution range in Eurasia. Positive cloacal swabs suggest that eagles can spread the virus with their faeces.

A novel European H5N8 influenza A virus has increased virulence in ducks but low zoonotic potential

We investigated in a unique setup of animal models and a human lung explant culture biological properties, including zoonotic potential, of a representative 2016 highly pathogenic avian influenza virus (HPAIV) H5N8, clade 2.3.4.4 group B (H5N8B), that spread rapidly in a huge and ongoing outbreak series in Europe and caused high mortality in waterfowl and domestic birds. HPAIV H5N8B showed increased virulence with rapid onset of severe disease and mortality in Pekin ducks due to pronounced neuro- and hepatotropism. Cross-species infection was evaluated in mice, ferrets, and in a human lung explant culture model. While the H5N8B isolate was highly virulent for Balb/c mice, virulence and transmissibility were grossly reduced in ferrets, which was mirrored by marginal replication in human lung cultures infected ex vivo. Our data indicate that the 2016 HPAIV H5N8B is avian-adapted with augmented virulence for waterfowl, but has low zoonotic potential. The here tested combination of animal studies with the inoculation of human explants provides a promising future workflow to evaluate zoonotic potential, mammalian replication competence and avian virulence of HPAIV.

Compatibility between haemagglutinin and neuraminidase drives the recent emergence of novel clade 2.3.4.4 H5Nx avian influenza viruses in China

Genetic reassortments between highly pathogenic avian influenza (HPAI) H5 subtype viruses with different neuraminidase (NA) subtypes have increased in prevalence since 2010 in wild birds and poultry from China. The HA gene slightly evolved from clade 2.3.4 to clade 2.3.4.4, raising the question of whether novel clade 2.3.4.4 HA broke the balance with N1 but is matched well with NAx to drive viral epidemics. To clarify the role of compatibility between HA and NA on the prevalence of H5Nx subtypes, we constructed 10 recombinant viruses in which the clade 2.3.4 or clade 2.3.4.4 HA genes were matched with different NA (N1, N2 and N8) genes and evaluated viral characteristics and pathogenicity. Combinations between clade 2.3.4 HA and N1 or between clade 2.3.4.4 HA and NAx, but not between clade 2.3.4.4 HA and N1, or between clade 2.3.4 HA and NAx, promoted viral growth, NA activity, thermostability, low-pH stability and pathogenicity in chicken and mice. These findings suggest that both clade 2.3.4 HA/N1 and clade 2.3.4.4 HA/NAx displayed a better match, which could promote the increased prevalence of clade 2.3.4 H5N1 AIV (prior to 2010) and clade 2.3.4.4 H5Nx AIV (since 2010) in China, respectively.

Avian influenza overview November 2017 - February 2018

Between 16 November 2017 and 15 February 2018, one highly pathogenic avian influenza (HPAI) A(H5N6) and five HPAI A(H5N8) outbreaks in poultry holdings, two HPAI A(H5N6) outbreaks in captive birds and 22 HPAI A(H5N6) wild bird events were reported within Europe. There is a lower incursion of HPAI A(H5N6) in poultry compared to HPAI A(H5N8). There is no evidence to date that HPAI A(H5N6) viruses circulating in Europe are associated with clades infecting humans. Clinical signs in ducks infected with HPAI A(H5N8) seemed to be decreasing, based on reports from Bulgaria. However, HPAI A(H5N8) is still present in Europe and is widespread in neighbouring areas. The majority of mortality events of wild birds from HPAIV A(H5) in this three-month period involved single birds. This indicates that the investigation of events involving single dead birds of target species is important for comprehensive passive surveillance for HPAI A(H5). Moreover, 20 low pathogenic avian influenza (LPAI) outbreaks were reported in three Member States. The risk of zoonotic transmission to the general public in Europe is considered to be very low. The first human case due to avian influenza A(H7N4) was notified in China underlining the threat that newly emerging avian influenza viruses pose for transmission to humans. Close monitoring is required of the situation in Africa and the Middle East with regards to HPAI A(H5N1) and A(H5N8). Uncontrolled spread of virus and subsequent further genetic evolution in regions geographically connected to Europe may increase uncertainty and risk for further dissemination of virus. The risk of HPAI introduction from Third countries via migratory wild birds to Europe is still considered much lower for wild birds crossing the southern borders compared to birds crossing the north-eastern borders, whereas the introduction via trade is still very to extremely unlikely.