Evidence for common ancestry among viruses isolated from wild birds in Beringia and highly pathogenic intercontinental reassortant H5N1 and H5N2 influenza A viruses

Molecular Characterization of Non-H5 and Non-H7 Avian Influenza Viruses from Non-Mallard Migratory Waterbirds of the North American Flyways, 2006-2011

The surveillance of migratory waterbirds (MWs) for avian influenza virus (AIV) is indispensable for the early detection of a potential AIV incursion into poultry. Surveying AIV infections and virus subtypes in understudied MW species could elucidate their role in AIV ecology. Oropharyngeal-cloacal (OPC) swabs were collected from non-mallard MWs between 2006 and 2011. OPC swabs (n = 1158) that molecularly tested positive for AIV (Cts ≤ 32) but tested negative for H5 and H7 subtypes were selected for virus isolation (VI). The selected samples evenly represented birds from all four North American flyways (Pacific, Central, Mississippi, and Atlantic). Eighty-seven low pathogenic AIV isolates, representing 31 sites in 17 states, were recovered from the samples. All isolates belonged to the North American lineage. The samples representing birds from the Central Flyway had the highest VI positive rate (57.5%) compared to those from the other flyways (10.3-17.2%), suggesting that future surveillance can focus on the Central Flyway. Of the isolates, 43.7%, 12.6%, and 10.3% were obtained from blue-winged teal, American wigeon, and American black duck species, respectively. Hatch-year MWs represented the majority of the isolates (70.1%). The most common H and N combinations were H3N8 (23.0%), H4N6 (18.4%), and H4N8 (18.4%). The HA gene between non-mallard and mallard MW isolates during the same time period shared 85.5-99.5% H3 identity and 89.3-99.7% H4 identity. Comparisons between MW (mallard and non-mallard) and poultry H3 and H4 isolates also revealed high similarity (79.0-99.0% and 88.7-98.4%), emphasizing the need for continued AIV surveillance in MWs.

Avian encephalomyelitis virus in backyard chickens

Background and Aim

Avian viral diseases usually cause high economic losses because of high morbidity and mortality and poor growth. The rearing of chickens in backyards could have an important role in the spread of certain diseases, particularly those of viral origin. Infected birds might be prone to many viral infections for several reasons, including a lack of vaccination programs, the mixing of different bird species in the same location, and the close interactions of these birds with wild and migratory birds carrying various pathogens. This study aimed to conduct serological surveillance of avian encephalomyelitis virus (AEV) in some backyard chickens in the eastern region of Saudi Arabia.

Materials and Methods

Serum samples (n = 368) were collected from domestic chickens reared in 10 backyards in the Eastern Province of Saudi Arabia. None of the domestic birds in these 10 backyards were vaccinated against the virus. In addition, 78 serum samples were collected from free-ranging birds belonging to Columbidae, such as pigeons and doves, in common areas near the domestic backyards. We tested these sera for specific antibodies against AEV.

Results

Our results revealed seroconversion to AEV among the examined chickens (14.6%). None of the tested pigeons and doves displayed seroconversion to AEV.

Conclusion

Seroconversion of these non-vaccinated birds against AEV was suggestive of a recent natural infection by this virus. Further studies with a large number of birds are required to molecularly characterize the circulating strains of this virus in this area.

Evidence of the circulation of avian metapneumovirus in domestic backyard chickens in Eastern Saudi Arabia in 2019

Background and Aim

Avian metapneumovirus (aMPV) is a recently discovered respiratory virus in chickens. Avian metapneumovirus has been linked to respiratory syndromes, reproductive failure in affected chickens and turkeys, swollen head syndrome in chickens, and rhinotracheitis in turkeys. Wild birds are considered potential reservoirs of aMPV, particularly aMPV-C. However, little is known about the prevalence of aMPV in Saudi Arabia. Considering the relevance of backyard chickens in the transmission and sustainability of certain avian viral diseases, this study aimed to assess aMPV exposure in backyard chickens and wild birds circulating near selected locations.

Materials and Methods

We collected 368 serum samples from unvaccinated backyard chickens in ten locations in Eastern Saudi Arabia. Furthermore, we collected 78 serum samples from species of free-ranging birds belonging to the Columbidae family, such as pigeons and doves, captured from the same areas. Using commercial enzyme-linked immunosorbent assay kits, we tested the sera of domestic backyard chickens and wild birds for antibodies against aMPV.

Results

Our results showed that 74/368 birds were positive for aMPV-related antibodies. Conversely, none of the tested wild birds seroconverted to aMPV.

Conclusion

The antibody titers detected in the backyard chickens suggested recent exposure to aMPV. Considering these results, further large-scale serological and molecular studies are needed to evaluate the prevalence of aMPV in these birds and characterize the circulating strains of aMPV in this region.

Global dissemination of influenza A virus is driven by wild bird migration through arctic and subarctic zones

Influenza A viruses (IAV) circulate endemically among many wild aquatic bird populations that seasonally migrate between wintering grounds in southern latitudes to breeding ranges along the perimeter of the circumpolar arctic. Arctic and subarctic zones are hypothesized to serve as ecologic drivers of the intercontinental movement and reassortment of IAVs due to high densities of disparate populations of long distance migratory and native bird species present during breeding seasons. Iceland is a staging ground that connects the East Atlantic and North Atlantic American flyways, providing a unique study system for characterizing viral flow between eastern and western hemispheres. Using Bayesian phylodynamic analyses, we sought to evaluate the viral connectivity of Iceland to proximal regions and how inter-species transmission and reassortment dynamics in this region influence the geographic spread of low and highly pathogenic IAVs. Findings demonstrate that IAV movement in the arctic and subarctic reflects wild bird migration around the perimeter of the circumpolar north, favouring short-distance flights between proximal regions rather than long distance flights over the polar interior. Iceland connects virus movement between mainland Europe and North America, consistent with the westward migration of wild birds from mainland Europe to Northeastern Canada and Greenland. Though virus diffusion rates were similar among avian taxonomic groups in Iceland, gulls play an outsized role as sinks of IAVs from other avian hosts prior to onward migration. These data identify patterns of virus movement in northern latitudes and inform future surveillance strategies related to seasonal and emergent IAVs with potential public health concern.

Pathways for avian influenza virus spread: GPS reveals wild waterfowl in commercial livestock facilities and connectivity with the natural wetland landscape

Zoonotic diseases are of considerable concern to the human population and viruses such as avian influenza (AIV) threaten food security, wildlife conservation and human health. Wild waterfowl and the natural wetlands they use are known AIV reservoirs, with birds capable of virus transmission to domestic poultry populations. While infection risk models have linked migration routes and AIV outbreaks, there is a limited understanding of wild waterfowl presence on commercial livestock facilities, and movement patterns linked to natural wetlands. We documented 11 wild waterfowl (three Anatidae species) in or near eight commercial livestock facilities in Washington and California with GPS telemetry data. Wild ducks used dairy and beef cattle feed lots and facility retention ponds during both day and night suggesting use for roosting and foraging. Two individuals (single locations) were observed inside poultry facility boundaries while using nearby wetlands. Ducks demonstrated high site fidelity, returning to the same areas of habitats (at livestock facilities and nearby wetlands), across months or years, showed strong connectivity with surrounding wetlands, and arrived from wetlands up to 1251 km away in the week prior. Telemetry data provides substantial advantages over observational data, allowing assessment of individual movement behaviour and wetland connectivity that has significant implications for outbreak management. Telemetry improves our understanding of risk factors for waterfowl-livestock virus transmission and helps identify factors associated with coincident space use at the wild waterfowl-domestic livestock interface. Our research suggests that even relatively small or isolated natural and artificial water or food sources in/near facilities increases the likelihood of attracting waterfowl, which has important consequences for managers attempting to minimize or prevent AIV outbreaks. Use and interpretation of telemetry data, especially in near-real-time, could provide key information for reducing virus transmission risk between waterfowl and livestock, improving protective barriers between wild and domestic species, and abating outbreaks.

Spatiotemporal changes in influenza A virus prevalence among wild waterfowl inhabiting the continental United States throughout the annual cycle

Avian influenza viruses can pose serious risks to agricultural production, human health, and wildlife. An understanding of viruses in wild reservoir species across time and space is important to informing surveillance programs, risk models, and potential population impacts for vulnerable species. Although it is recognized that influenza A virus prevalence peaks in reservoir waterfowl in late summer through autumn, temporal and spatial variation across species has not been fully characterized. We combined two large influenza databases for North America and applied spatiotemporal models to explore patterns in prevalence throughout the annual cycle and across the continental United States for 30 waterfowl species. Peaks in prevalence in late summer through autumn were pronounced for dabbling ducks in the genera Anas and Spatula, but not Mareca. Spatially, areas of high prevalence appeared to be related to regional duck density, with highest predicted prevalence found across the upper Midwest during early fall, though further study is needed. We documented elevated prevalence in late winter and early spring, particularly in the Mississippi Alluvial Valley. Our results suggest that spatiotemporal variation in prevalence outside autumn staging areas may also represent a dynamic parameter to be considered in IAV ecology and associated risks.

Epidemiology and Ecology of Influenza A Viruses among Wildlife in the Arctic

Arctic regions are ecologically significant for the environmental persistence and geographic dissemination of influenza A viruses (IAVs) by avian hosts and other wildlife species. Data describing the epidemiology and ecology of IAVs among wildlife in the arctic are less frequently published compared to southern temperate regions, where prevalence and subtype diversity are more routinely documented. Following PRISMA guidelines, this systematic review addresses this gap by describing the prevalence, spatiotemporal distribution, and ecological characteristics of IAVs detected among wildlife and the environment in this understudied region of the globe. The literature search was performed in PubMed and Google Scholar using a set of pre-defined search terms to identify publications reporting on IAVs in Arctic regions between 1978 and February 2022. A total of 2125 articles were initially screened, 267 were assessed for eligibility, and 71 articles met inclusion criteria. IAVs have been detected in multiple wildlife species in all Arctic regions, including seabirds, shorebirds, waterfowl, seals, sea lions, whales, and terrestrial mammals, and in the environment. Isolates from wild birds comprise the majority of documented viruses derived from wildlife; however, among all animals and environmental matrices, 26 unique low and highly pathogenic subtypes have been characterized in the scientific literature from Arctic regions. Pooled prevalence across studies indicates 4.23% for wild birds, 3.42% among tested environmental matrices, and seroprevalences of 9.29% and 1.69% among marine and terrestrial mammals, respectively. Surveillance data are geographically biased, with most data from the Alaskan Arctic and many fewer reports from the Russian, Canadian, North Atlantic, and Western European Arctic. We highlight multiple important aspects of wildlife host, pathogen, and environmental ecology of IAVs in Arctic regions, including the role of avian migration and breeding cycles for the global spread of IAVs, evidence of inter-species and inter-continental reassortment at high latitudes, and how climate change-driven ecosystem shifts, including changes in the seasonal availability and distribution of dietary resources, have the potential to alter host–pathogen–environment dynamics in Arctic regions. We conclude by identifying gaps in knowledge and propose priorities for future research.

Ecological divergence of wild birds drives avian influenza spillover and global spread

The diversity of influenza A viruses (IAV) is primarily hosted by two highly divergent avian orders: Anseriformes (ducks, swans and geese) and Charadriiformes (gulls, terns and shorebirds). Studies of IAV have historically focused on Anseriformes, specifically dabbling ducks, overlooking the diversity of hosts in nature, including gull and goose species that have successfully adapted to human habitats. This study sought to address this imbalance by characterizing spillover dynamics and global transmission patterns of IAV over 10 years at greater taxonomic resolution than previously considered. Furthermore, the circulation of viral subtypes in birds that are either host-adapted (low pathogenic H13, H16) or host-generalist (highly pathogenic avian influenza—HPAI H5) provided a unique opportunity to test and extend models of viral evolution. Using Bayesian phylodynamic modelling we uncovered a complex transmission network that relied on ecologically divergent bird hosts. The generalist subtype, HPAI H5 was driven largely by wild geese and swans that acted as a source for wild ducks, gulls, land birds, and domestic geese. Gulls were responsible for moving HPAI H5 more rapidly than any other host, a finding that may reflect their long-distance, pelagic movements and their immuno-naïve status against this subtype. Wild ducks, long viewed as primary hosts for spillover, occupied an optimal space for viral transmission, contributing to geographic expansion and rapid dispersal of HPAI H5. Evidence of inter-hemispheric dispersal via both the Pacific and Atlantic Rims was detected, supporting surveillance at high latitudes along continental margins to achieve early detection. Both neutral (geographic expansion) and non-neutral (antigenic selection) evolutionary processes were found to shape subtype evolution which manifested as unique geographic hotspots for each subtype at the global scale. This study reveals how a diversity of avian hosts contribute to viral spread and spillover with the potential to improve surveillance in an era of rapid global change.

Our study provides novel insights into the biology of influenza A virus (IAV), which is timely in view of the unusually large number of animal and human cases of highly pathogenic avian influenza (HPAI) H5 across Europe, Asia, Africa and North America. Currently we face challenges with predicting how the avian reservoir will influence IAV spread because the mechanisms by which different subtypes disperse are not well understood. Our study sought to address this knowledge gap by systematically comparing the evolutionary dynamics that drive IAV transmission across subtypes and bird hosts with the goal of identifying spillover pathways at the wild-domestic interface. By analyzing the evolution of IAV over 10 years at greater taxonomic resolution than previously considered, we uncovered a complex transmission network that relied on ecologically divergent bird hosts. Domestic birds were responsible for slow but steady range expansion of HPAI H5, while wild birds such as geese, swans, gulls and ducks contibuted to rapid but episodic dispersal via uniquely different pathways. By assessing how virus-host systems are coupled, findings from this study have the potential to refine and enhance global surveillance and outbreak prediction.

Comparative pathogenicity and environmental transmission of recent highly pathogenic avian influenza H5 viruses

Strategies to control spread of highly pathogenic avian influenza (HPAI) viruses by wild birds appear limited, hence timely characterization of novel viruses is important to mitigate the risk for the poultry sector and human health. In this study we characterize three recent H5-clade 2.3.4.4 viruses, the H5N8-2014 group A virus and the H5N8-2016 and H5N6-2017 group B viruses. The pathogenicity of the three viruses for chickens, Pekin ducks and Eurasian wigeons was compared. The three viruses were highly pathogenic for chickens, but the two H5N8 viruses caused no to mild clinical symptoms in both duck species. The highest pathogenicity for duck species was observed for the most recent H5N6-2017 virus. For both duck species, virus shedding from the cloaca was higher after infection with group B viruses compared to the H5N8-2014 group A virus. Higher cloacal virus shedding of wild ducks may increase transmission between wild birds and poultry. Environmental transmission of H5N8-2016 virus to chickens was studied, which showed that chickens are efficiently infected by (fecal) contaminated water. These results suggest that pathogenicity of HPAI H5 viruses and virus shedding for ducks is evolving, which may have implications for the risk of introduction of these viruses into the poultry sector.

Highly pathogenic avian influenza virus H5N2 (clade 2.3.4.4) challenge of mallards age appropriate to the 2015 midwestern poultry outbreak

Background

The 2015 highly pathogenic avian influenza virus (HPAIV) H5N2 clade 2.3.4.4 outbreak in upper midwestern U.S. poultry operations was not detected in wild birds to any great degree during the outbreak, despite wild waterfowl being implicated in the introduction, reassortment, and movement of the virus into North America from Asia. This outbreak led to the demise of over 50 million domestic birds and occurred mainly during the northward spring migration of adult avian populations.

Objectives

There have been no experimental examinations of the pathogenesis, transmission, and population impacts of this virus in adult wild waterfowl with varying exposure histories—the most relevant age class.

Methods

We captured, housed, and challenged adult wild mallards (Anas platyrhynchos) with HPAIV H5N2 clade 2.3.4.4 and measured viral infection, viral excretion, and transmission to other mallards.

Results

All inoculated birds became infected and excreted moderate amounts of virus, primarily orally, for up to 14 days. Cohoused, uninoculated birds also all became infected. Serological status had no effect on susceptibility. There were no obvious clinical signs of disease, and all birds survived to the end of the study (14 days).

Conclusions

Based on these results, adult mallards are viable hosts of HPAIV H5N2 regardless of prior exposure history and are capable of transporting the virus over short and long distances. These findings have implications for surveillance efforts. The capture and sampling of wild waterfowl in the spring, when most surveillance programs are not operating, are important to consider in the design of future HPAIV surveillance programs.

Isolation of clade 2.3.4.4b A(H5N8), a highly pathogenic avian influenza virus, from a worker during an outbreak on a poultry farm, Russia, December 2020

This study presents the isolation of influenza A(H5N8) virus clade 2.3.4.4b from a poultry worker during an outbreak of highly pathogenic avian influenza A(H5N8) among chickens at a poultry farm in Astrakhan, Russia in December 2020. Nasopharyngeal swabs collected from seven poultry workers were positive for influenza A(H5N8), as confirmed by RT-PCR and sequencing. The influenza A(H5N8) virus was isolated from one of the human specimens and characterised. Sporadic human influenza A(H5)2.3.4.4. infections represent a possible concern for public health.

Ecology of Influenza A Viruses in Wild Birds and Wetlands of Alaska

Alaska represents a globally important region for the ecology of avian-origin influenza A viruses (IAVs) given the expansive wetlands in this region, which serve as habitat for numerous hosts of IAVs that disperse among four continents during the annual cycle. Extensive sampling of wild birds for IAVs in Alaska since 1991 has greatly extended inference regarding intercontinental viral exchange between North America and East Asia and the importance of Beringian endemic species to IAV ecology within this region. Data on IAVs in aquatic birds inhabiting Alaska have also been useful for helping to establish global patterns of prevalence in wild birds and viral dispersal across the landscape. In this review, we summarize the main findings from investigations of IAVs in wild birds and wetlands of Alaska with the aim of providing readers with an understanding of viral ecology within this region. More specifically, we review viral detections, evidence of IAV exposure, and genetic characterization of isolates derived from wild bird samples collected in Alaska by host taxonomy. Additionally, we provide a short overview of wetland complexes within Alaska that may be important to IAV ecology at the continental scale.

A Review of Pathogen Transmission at the Backyard Chicken-Wild Bird Interface

Habitat conversion and the expansion of domesticated, invasive species into native habitats are increasingly recognized as drivers of pathogen emergence at the agricultural-wildlife interface. Poultry agriculture is one of the largest subsets of this interface, and pathogen spillover events between backyard chickens and wild birds are becoming more commonly reported. Native wild bird species are under numerous anthropogenic pressures, but the risks of pathogen spillover from domestic chickens have been historically underappreciated as a threat to wild birds. Now that the backyard chicken industry is one of the fastest growing industries in the world, it is imperative that the principles of biosecurity, specifically bioexclusion and biocontainment, are legislated and implemented. We reviewed the literature on spillover events of pathogens historically associated with poultry into wild birds. We also reviewed the reasons for biosecurity failures in backyard flocks that lead to those spillover events and provide recommendations for current and future backyard flock owners.

The Genome Sequence of an H6N5 Influenza A Virus Strain Isolated from a Northern Pintail (Anas acuta) Sampled in Alaska, USA, Shares High Identity with That of a South Korean Wild Bird Strain

We report the genome sequence of an H6N5 influenza A virus isolated from a northern pintail sampled in Alaska in 2017. All segment sequences shared >99% nucleotide identity with those of a wild bird strain from South Korea. This finding supports viral dispersal between East Asia and North America by wild birds.

Waterfowl occurrence and residence time as indicators of H5 and H7 avian influenza in North American Poultry

Avian influenza (AI) affects wild aquatic birds and poses hazards to human health, food security, and wildlife conservation globally. Accordingly, there is a recognized need for new methods and tools to help quantify the dynamic interaction between wild bird hosts and commercial poultry. Using satellite-marked waterfowl, we applied Bayesian joint hierarchical modeling to concurrently model species distributions, residency times, migration timing, and disease occurrence probability under an integrated animal movement and disease distribution modeling framework. Our results indicate that migratory waterfowl are positively related to AI occurrence over North America such that as waterfowl occurrence probability or residence time increase at a given location, so too does the chance of a commercial poultry AI outbreak. Analyses also suggest that AI occurrence probability is greatest during our observed waterfowl northward migration, and less during the southward migration. Methodologically, we found that when modeling disparate facets of disease systems at the wildlife-agriculture interface, it is essential that multiscale spatial patterns be addressed to avoid mistakenly inferring a disease process or disease-environment relationship from a pattern evaluated at the improper spatial scale. The study offers important insights into migratory waterfowl ecology and AI disease dynamics that aid in better preparing for future outbreaks.

LIMITED DETECTION OF ANTIBODIES TO CLADE 2.3.4.4 A/GOOSE/GUANGDONG/1/1996 LINEAGE HIGHLY PATHOGENIC H5 AVIAN INFLUENZA VIRUS IN NORTH AMERICAN WATERFOWL

During 2014, highly pathogenic (HP) influenza A viruses (IAVs) of the A/Goose/Guangdong/1/1996 lineage (GsGD-HP-H5), originating from Asia, were detected in domestic poultry and wild birds in Canada and the US. These clade 2.3.4.4 GsGD-HP-H5 viruses included reassortants possessing North American lineage gene segments; were detected in wild birds in the Pacific, Central, and Mississippi flyways; and caused the largest HP IAV outbreak in poultry in US history. To determine if an antibody response indicative of previous infection with clade 2.3.4.4 GsGD-HP-H5 IAV could be detected in North American wild waterfowl sampled before, during, and after the 2014-15 outbreak, sera from 2,793 geese and 3,715 ducks were tested by blocking enzyme-linked immunosorbent assay and hemagglutination inhibition (HI) tests using both clade 2.3.4.4 GsGD-HPH5 and North American lineage low pathogenic (LP) H5 IAV antigens. We detected an antibody response meeting a comparative titer-based criteria (HI titer observed with 2.3.4.4 GsGD-HP-H5 antigens exceeded the titer observed for LP H5 antigen by two or more dilutions) for previous infection with clade 2.3.4.4 GsGD-HP-H5 IAV in only five birds, one Blue-winged Teal (Spatula discors) sampled during the outbreak and three Mallards (Anas platyrhynchos) and one Canada Goose (Branta canadensis) sampled during the post-outbreak period. These serologic results are consistent with the spatiotemporal extent of the outbreak in wild birds in North America during 2014 and 2015 and limited exposure of waterfowl to GsGD-HP-H5 IAV, particularly in the central and eastern US.

Confronting models with data: the challenges of estimating disease spillover

For pathogens known to transmit across host species, strategic investment in disease control requires knowledge about where and when spillover transmission is likely. One approach to estimating spillover is to directly correlate observed spillover events with covariates. An alternative is to mechanistically combine information on host density, distribution and pathogen prevalence to predict where and when spillover events are expected to occur. We use several case studies at the wildlife-livestock disease interface to highlight the challenges, and potential solutions, to estimating spatio-temporal variation in spillover risk. Datasets on multiple host species often do not align in space, time or resolution, and may have no estimates of observation error. Linking these datasets requires they be related to a common spatial and temporal resolution and appropriately propagating errors in predictions can be difficult. Hierarchical models are one potential solution, but for fine-resolution predictions at broad spatial scales, many models become computationally challenging. Despite these limitations, the confrontation of mechanistic predictions with observed events is an important avenue for developing a better understanding of pathogen spillover. Systems where data have been collected at all levels in the spillover process are rare, or non-existent, and require investment and sustained effort across disciplines. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.

Emperor geese (Anser canagicus) are exposed to a diversity of influenza A viruses, are infected during the non-breeding period and contribute to intercontinental viral dispersal

Emperor geese (Anser canagicus) are endemic to coastal areas within Beringia and have previously been found to have antibodies to or to be infected with influenza A viruses (IAVs) in Alaska. In this study, we use virological, serological and tracking data to further elucidate the role of emperor geese in the ecology of IAVs in Beringia during the non-breeding period. Specifically, we assess evidence for: (a) active IAV infection during spring staging, autumn staging and wintering periods; (b) infection with novel Eurasian-origin or interhemispheric reassortant viruses; (c) contemporary movement of geese between East Asia and North America; (d) previous exposure to viruses of 14 haemagglutinin subtypes, including Eurasian lineage highly pathogenic (HP) H5 IAVs; and (e) subtype-specific antibody seroconversion and seroreversion. Emperor geese were found to shed IAVs, including interhemispheric reassortant viruses, throughout the non-breeding period; migrate between Alaska and the Russian Far East prior to and following remigial moult; have antibodies reactive to a diversity of IAVs including, in a few instances, Eurasian lineage HP H5 IAVs; and exhibit relatively broad and stable patterns of population immunity among breeding females. Results of this study suggest that emperor geese may play an important role in the maintenance and dispersal of IAVs within Beringia during the non-breeding period and provide information that may be used to further optimize surveillance activities focused on the early detection of Eurasian-origin IAVs in North America.

Introduction of Eurasian-Origin Influenza A(H8N4) Virus into North America by Migratory Birds

We identified a Eurasian-origin influenza A(H8N4) virus in North America by sampling wild birds in western Alaska, USA. Evidence for repeated introductions of influenza A viruses into North America by migratory birds suggests that intercontinental dispersal might not be exceedingly rare and that our understanding of viral establishment is incomplete.

Transmission Dynamics of Highly Pathogenic Avian Influenza Virus A(H5Nx) Clade 2.3.4.4, North America, 2014-2015

Eurasia highly pathogenic avian influenza virus (HPAIV) H5 clade 2.3.4.4 emerged in North America at the end of 2014 and caused outbreaks affecting >50 million poultry in the United States before eradication in June 2015. We investigated the underlying ecologic and epidemiologic processes associated with this viral spread by performing a comparative genomic study using 268 full-length genome sequences and data from outbreak investigations. Reassortant HPAIV H5N2 circulated in wild birds along the Pacific flyway before several spillover events transmitting the virus to poultry farms. Our analysis suggests that >3 separate introductions of HPAIV H5N2 into Midwest states occurred during March–June 2015; transmission to Midwest poultry farms from Pacific wild birds occurred ≈1.7–2.4 months before detection. Once established in poultry, the virus rapidly spread between turkey and chicken farms in neighboring states. Enhanced biosecurity is required to prevent the introduction and dissemination of HPAIV across the poultry industry.

Isolation and characterization of H5Nx highly pathogenic avian influenza viruses of clade 2.3.4.4 in Russia

In 2016-2017, several subtypes of the highly pathogenic avian influenza (HPAI) virus were isolated on the territory of Russia. In the autumn of 2016, during the avian influenza virus surveillance in the territory of the Kamchatka region of Russia the HPAI A(H5N5) influenza virus was isolated. Then, during 2016-2017, multiple outbreaks among wild birds and poultry caused by HPAI A(H5N8) avian influenza virus were recorded in European part of Russia. At the end of 2017, an outbreak among poultry caused by HPAI A(H5N2) influenza virus was recorded in the European part of Russia. Phylogenetic analysis of HA of the A(H5N5), A(H5N8), A(H5N2) showed the strains belong to the clade 2.3.4.4 b. All isolated strains were antigenically closely related to candidate vaccine viruses of clade 2.3.4.4 and showed high virulence in mice. Genetic analysis revealed presence of genetic markers potentially related to high virulence in mice in all studied viruses.

Genetic characterization of an avian H4N6 influenza virus isolated from the Izumi plain, Japan

An influenza A virus of H4N6 subtype was isolated from the Izumi plain, Japan, in 2013. Genetic analyses revealed that two viral genes (M and NS gene segments) of this isolate were genetically distinct from those of the H4N6 virus isolated from the same place in 2012. Furthermore, three viral genes (PB2, PB1 and M gene segments) of this isolate share high similarity with those of the North American isolates of 2014. These results suggest a high frequency of genetic reassortment of avian influenza viruses in Asian waterfowl and intercontinental movements of avian influenza viruses via migratory waterfowl.

Experimental infection of H5N1 and H5N8 highly pathogenic avian influenza viruses in Northern Pintail (Anas acuta)

The wide geographic spread of Eurasian Goose/Guangdong lineage highly pathogenic avian influenza (HPAI) clade 2.3.4.4 viruses by wild birds is of great concern. In December 2014, an H5N8 HPAI clade 2.3.4.4 Group A (2.3.4.4A) virus was introduced to North America. Long-distance migratory wild aquatic birds between East Asia and North America, such as Northern Pintail (Anas acuta), were strongly suspected of being a source of intercontinental transmission. In this study, we evaluated the pathogenicity, infectivity and transmissibility of an H5N8 HPAI clade 2.3.4.4A virus in Northern Pintails and compared the results to that of an H5N1 HPAI clade 2.3.2.1 virus. All of Northern Pintails infected with either H5N1 or H5N8 virus lacked clinical signs and mortality, but the H5N8 clade 2.3.4.4 virus was more efficient at replicating within and transmitting between Northern Pintails than the H5N1 clade 2.3.2.1 virus. The H5N8-infected birds shed high titre of viruses from oropharynx and cloaca, which in the field supported virus transmission and spread. This study highlights the role of wild waterfowl in the intercontinental spread of some HPAI viruses. Migratory aquatic birds should be carefully monitored for the early detection of H5 clade 2.3.4.4 and other HPAI viruses.

Influenza A virus recovery, diversity, and intercontinental exchange: A multi-year assessment of wild bird sampling at Izembek National Wildlife Refuge, Alaska

Western Alaska is a potential point-of-entry for foreign-origin influenza A viruses (IAVs) into North America via migratory birds. We sampled waterfowl and gulls for IAVs at Izembek National Wildlife Refuge (NWR) in western Alaska, USA, during late summer and autumn months of 2011-2015, to evaluate the abundance and diversity of viruses at this site. We collected 4842 samples across five years from 25 species of wild birds resulting in the recovery, isolation, and sequencing of 172 IAVs. With the intent of optimizing sampling efficiencies, we used information derived from this multi-year effort to: 1) evaluate from which species we consistently recover viruses, 2) describe viral subtypes of isolates by host species and year, 3) characterize viral gene segment sequence diversity with respect to host species, and assess potential differences in the viral lineages among the host groups, and 4) examine how evidence of intercontinental exchange of IAVs relates to host species. We consistently recovered viruses from dabbling ducks (Anas spp.), emperor geese (Chen canagica) and glaucous-winged gulls (Larus glaucescens). There was little evidence for differences in viral subtypes and diversity from different waterfowl hosts, however subtypes and viral diversity varied between waterfowl host groups and glaucous-winged gulls. Furthermore, higher proportions of viral sequences from northern pintails (Anas acuta), emperor geese and glaucous-winged gulls were grouped in phylogenetic clades that included IAV sequences originating from wild birds sampled in Asia as compared to non-pintail dabbling ducks, a difference that may be related to intercontinental migratory tendencies of host species. Our summary of research and surveillance efforts at Izembek NWR will assist in future prioritization of which hosts to sample and swab types to collect in Alaska and elsewhere in order to maximize isolate recovery, subtype and sequence diversity for resultant viruses, and detection of evidence for intercontinental viral exchange.

Reoccurrence of Avian Influenza A(H5N2) Virus Clade 2.3.4.4 in Wild Birds, Alaska, USA, 2016

We report reoccurrence of highly pathogenic avian influenza A(H5N2) virus clade 2.3.4.4 in a wild mallard in Alaska, USA, in August 2016. Identification of this virus in a migratory species confirms low-frequency persistence in North America and the potential for re-dissemination of the virus during the 2016 fall migration.

Lessons learned from research and surveillance directed at highly pathogenic influenza A viruses in wild birds inhabiting North America

Following detections of highly pathogenic (HP) influenza A viruses (IAVs) in wild birds inhabiting East Asia after the turn of the millennium, the intensity of sampling of wild birds for IAVs increased throughout much of North America. The objectives for many research and surveillance efforts were directed towards detecting Eurasian origin HP IAVs and understanding the potential of such viruses to be maintained and dispersed by wild birds. In this review, we highlight five important lessons learned from research and surveillance directed at HP IAVs in wild birds inhabiting North America: (1) Wild birds may disperse IAVs between North America and adjacent regions via migration, (2) HP IAVs can be introduced to wild birds in North America, (3) HP IAVs may cross the wild bird-poultry interface in North America, (4) The probability of encountering and detecting a specific virus may be low, and (5) Population immunity of wild birds may influence HP IAV outbreaks in North America. We review empirical support derived from research and surveillance efforts for each lesson learned and, furthermore, identify implications for future surveillance efforts, biosecurity, and population health. We conclude our review by identifying five additional areas in which we think future mechanistic research relative to IAVs in wild birds in North America are likely to lead to other important lessons learned in the years ahead.

Reassortment of Influenza A Viruses in Wild Birds in Alaska before H5 Clade 2.3.4.4 Outbreaks

Sampling of mallards in Alaska during September 2014-April 2015 identified low pathogenic avian influenza A virus (subtypes H5N2 and H1N1) that shared ancestry with highly pathogenic reassortant H5N2 and H5N1 viruses. Molecular dating indicated reassortment soon after interhemispheric movement of H5N8 clade 2.3.4.4, suggesting genetic exchange in Alaska or surrounds before outbreaks.

Spatial transmission of H5N6 highly pathogenic avian influenza viruses among wild birds in Ibaraki Prefecture, Japan, 2016-2017

From 29 November 2016 to 24 January 2017, sixty-three cases of H5N6 highly pathogenic avian influenza virus (HPAIV) infections were detected in wild birds in Ibaraki Prefecture, Japan. Here, we analyzed the genetic, temporal, and geographic correlations of these 63 HPAIVs to elucidate their dissemination throughout the prefecture. Full-genome sequence analysis of the Ibaraki isolates showed that 7 segments (PB2, PB1, PA, HA, NP, NA, NS) were derived from G1.1.9 strains while the M segment was from G1.1 strains; both groups of strains circulated in south China. Pathological studies revealed severe systemic infection in dead swans (the majority of dead birds and the only species necropsied), thus indicating high susceptibility to H5N6 HPAIVs. Coalescent phylogenetic analysis using the 7 G1.1.9-derived segments enabled detailed analysis of the short-term evolution of these highly homologous HPAIVs. This analysis revealed that the H5N6 HPAIVs isolated from wild birds in Ibaraki Prefecture were divided into 7 groups. Spatial analysis demonstrated that most of the cases concentrated around Senba Lake originated from a single source, and progeny viruses were transmitted to other locations after the infection expanded in mute swans. In contrast, within just a 5-km radius of the area in which cases were concentrated, three different intrusions of H5N6 HPAIVs were evident. Multi-segment analysis of short-term evolution showed that not only was the invading virus spread throughout Ibaraki Prefecture but also that, despite the small size of this region, multiple invasions had occurred during winter 2016-2017.

Pathobiology of Clade 2.3.4.4 H5Nx High-Pathogenicity Avian Influenza Virus Infections in Minor Gallinaceous Poultry Supports Early Backyard Flock Introductions in the Western United States in 2014-2015

In 2014 and 2015, the United States experienced an unprecedented outbreak of Eurasian clade 2.3.4.4 H5 highly pathogenic avian influenza (HPAI) virus. Initial cases affected mainly wild birds and mixed backyard poultry species, while later outbreaks affected mostly commercial chickens and turkeys. The pathogenesis, transmission, and intrahost evolutionary dynamics of initial Eurasian H5N8 and reassortant H5N2 clade 2.3.4.4 HPAI viruses in the United States were investigated in minor gallinaceous poultry species (i.e., species for which the U.S. commercial industries are small), namely, Japanese quail, bobwhite quail, pearl guinea fowl, chukar partridges, and ring-necked pheasants. Low mean bird infectious doses (<2 to 3.7 log₁₀) support direct introduction and infection of these species as observed in mixed backyard poultry during the early outbreaks. Pathobiological features and systemic virus replication in all species tested were consistent with HPAI virus infection. Sustained virus shedding with transmission to contact-exposed birds, alongside long incubation periods, may enable unrecognized dissemination and adaptation to other gallinaceous species, such as chickens and turkeys. Genome sequencing of excreted viruses revealed numerous low-frequency polymorphisms and 20 consensus-level substitutions in all genes and species, but especially in Japanese quail and pearl guinea fowl and in internal proteins PB1 and PB2. This genomic flexibility after only one passage indicates that influenza viruses can continue to evolve in galliform species, increasing their opportunity to adapt to other species. Our findings suggest that these gallinaceous poultry are permissive for infection and sustainable transmissibility with the 2014 initial wild bird-adapted clade 2.3.4.4 virus, with potential acquisition of mutations leading to host range adaptation.IMPORTANCE The outbreak of clade 2.3.4.4 H5 highly pathogenic avian influenza (HPAI) virus that occurred in the United States in 2014 and 2015 represents the worst livestock disease event in the country, with unprecedented socioeconomic and commercial consequences. Epidemiological and molecular investigations can identify transmission pathways of the HPAI virus. However, understanding the pathogenesis, transmission, and intrahost evolutionary dynamics of new HPAI viruses in different avian species is paramount. The significance of our research is in examining the susceptibility of minor gallinaceous species to HPAI virus, as this poultry sector also suffers from HPAI epizootics, and identifying the biological potential of these species as an epidemiological link between the waterfowl reservoir and the commercial chicken and turkey populations, with the ultimate goal of refining surveillance in these populations to enhance early detection, management, and control in future HPAI virus outbreaks.

Surveillance for highly pathogenic influenza A viruses in California during 2014-2015 provides insights into viral evolutionary pathways and the spatiotemporal extent of viruses in the Pacific Americas Flyway

We used surveillance data collected in California before, concurrent with, and subsequent to an outbreak of highly pathogenic (HP) clade 2.3.4.4 influenza A viruses (IAVs) in 2014–2015 to (i) evaluate IAV prevalence in waterfowl, (ii) assess the evidence for spill-over infections in marine mammals and (iii) genetically characterize low-pathogenic (LP) and HP IAVs to refine inference on the spatiotemporal extent of HP genome constellations and to evaluate possible evolutionary pathways. We screened samples from 1496 waterfowl and 1142 marine mammals collected from April 2014 to August 2015 and detected IAV RNA in 159 samples collected from birds (n=157) and pinnipeds (n=2). HP IAV RNA was identified in three samples originating from American wigeon (Anas americana). Genetic sequence data were generated for a clade 2.3.4.4 HP IAV-positive diagnostic sample and 57 LP IAV isolates. Phylogenetic analyses revealed that the HP IAV was a reassortant H5N8 virus with gene segments closely related to LP IAVs detected in mallards (Anas platyrhynchos) sampled in California and other IAVs detected in wild birds sampled within the Pacific Americas Flyway. In addition, our analysis provided support for common ancestry between LP IAVs recovered from waterfowl sampled in California and gene segments of reassortant HP H5N1 IAVs detected in British Columbia, Canada and Washington, USA. Our investigation provides evidence that waterfowl are likely to have played a role in the evolution of reassortant HP IAVs in the Pacific Americas Flyway during 2014–2015, whereas we did not find support for spill-over infections in potential pinniped hosts.

The Role of Clinical Virology Laboratory and the Clinical Virology Laboratorian in Ensuring Effective Surveillance for Influenza and Other Respiratory Viruses: Points to Consider and Pitfalls to Avoid

Influenza and respiratory viruses have a global impact on public health. Clinical virology laboratories and laboratorians play an important role in not only the diagnosis but also the surveillance of these pathogens. Surveillance for influenza and other respiratory pathogens is important, as it informs public health decision making in terms of influenza vaccine and antiviral effectiveness, informs clinicians and public health practitioners about the pathogenicity of specific viral strains, guides clinical practice, and supports laboratory panning activities. Key background issues include the following: the fact that the laboratory is only one of several data providers to a surveillance system, the biologic nature of influenza and respiratory viruses and the laboratory needs to keep up to date on the diagnosis of these agents, the need for laboratorians to be involved in case definition development, the impact of push and pull data flow models on laboratory resources, and the fact that laboratories may be asked to provide more than just test results to surveillance programs. This review also identifies some key issues or questions that arise during the pre-analytic, analytic, and post-analytic phases that could impact on the ability of the laboratory to link to surveillance programs. Finally, issues surrounding virus characterization programs and how they link to surveillance programs are identified and discussed.

Evidence for wild waterfowl origin of H7N3 influenza A virus detected in captive-reared New Jersey pheasants

In August 2014, a low-pathogenic H7N3 influenza A virus was isolated from pheasants at a New Jersey gamebird farm and hunting preserve. In this study, we use phylogenetic analyses and calculations of genetic similarity to gain inference into the genetic ancestry of this virus and to identify potential routes of transmission. Results of maximum-likelihood (ML) and maximum-clade-credibility (MCC) phylogenetic analyses provide evidence that A/pheasant/New Jersey/26996-2/2014 (H7N3) had closely related H7 hemagglutinin (HA) and N3 neuraminidase (NA) gene segments as compared to influenza A viruses circulating among wild waterfowl in the central and eastern USA. The estimated time of the most recent common ancestry (TMRCA) between the pheasant virus and those most closely related from wild waterfowl was early 2013 for both the H7 HA and N3 NA gene segments. None of the viruses from waterfowl identified as being most closely related to A/pheasant/New Jersey/26996-2/2014 at the HA and NA gene segments in ML and MCC phylogenetic analyses shared ≥99 % nucleotide sequence identity for internal gene segment sequences. This result indicates that specific viral strains identified in this study as being closely related to the HA and NA gene segments of A/pheasant/New Jersey/26996-2/2014 were not the direct predecessors of the etiological agent identified during the New Jersey outbreak. However, the recent common ancestry of the H7 and N3 gene segments of waterfowl-origin viruses and the virus isolated from pheasants suggests that viral diversity maintained in wild waterfowl likely played an important role in the emergence of A/pheasant/New Jersey/26996-2/2014.

Surveillance for Eurasian-origin and intercontinental reassortant highly pathogenic influenza A viruses in Alaska, spring and summer 2015

BACKGROUND

Eurasian-origin and intercontinental reassortant highly pathogenic (HP) influenza A viruses (IAVs) were first detected in North America in wild, captive, and domestic birds during November-December 2014. Detections of HP viruses in wild birds in the contiguous United States and southern Canadian provinces continued into winter and spring of 2015 raising concerns that migratory birds could potentially disperse viruses to more northerly breeding areas where they could be maintained to eventually seed future poultry outbreaks.

RESULTS

We sampled 1,129 wild birds on the Yukon-Kuskokwim Delta, Alaska, one of the largest breeding areas for waterfowl in North America, during spring and summer of 2015 to test for Eurasian lineage and intercontinental reassortant HP H5 IAVs and potential progeny viruses. We did not detect HP IAVs in our sample collection from western Alaska; however, we isolated five low pathogenic (LP) viruses. Four isolates were of the H6N1 (n = 2), H6N2, and H9N2 combined subtypes whereas the fifth isolate was a mixed infection that included H3 and N7 gene segments. Genetic characterization of these five LP IAVs isolated from cackling (Branta hutchinsii; n = 2) and greater white-fronted geese (Anser albifrons; n = 3), revealed three viral gene segments sharing high nucleotide identity with HP H5 viruses recently detected in North America. Additionally, one of the five isolates was comprised of multiple Eurasian lineage gene segments.

CONCLUSIONS

Our results did not provide direct evidence for circulation of HP IAVs in the Yukon-Kuskokwim Delta region of Alaska during spring and summer of 2015. Prevalence and genetic characteristics of LP IAVs during the sampling period are concordant with previous findings of relatively low viral prevalence in geese during spring, non-detection of IAVs in geese during summer, and evidence for intercontinental exchange of viruses in western Alaska.