Prevalence and control of H7 avian influenza viruses in birds and humans

SUMMARYThe H7 subtype HA gene has been found in combination with all nine NA subtype genes. Most exhibit low pathogenicity and only rarely high pathogenicity in poultry (and humans). During the past few years infections of poultry and humans with H7 subtypes have increased markedly. This review summarizes the emergence of avian influenza virus H7 subtypes in birds and humans, and the possibilities of its control in poultry. All H7Nx combinations were reported from wild birds, the natural reservoir of the virus. Geographically, the most prevalent subtype is H7N7, which is endemic in wild birds in Europe and was frequently reported in domestic poultry, whereas subtype H7N3 is mostly isolated from the Americas. In humans, mild to fatal infections were caused by subtypes H7N2, H7N3, H7N7 and H7N9. While infections of humans have been associated mostly with exposure to domestic poultry, infections of poultry have been linked to wild birds or live-bird markets. Generally, depopulation of infected poultry was the main control tool; however, inactivated vaccines were also used. In contrast to recent cases caused by subtype H7N9, human infections were usually self-limiting and rarely required antiviral medication. Close genetic and antigenic relatedness of H7 viruses of different origins may be helpful in development of universal vaccines and diagnostics for both animals and humans. Due to the wide spread of H7 viruses and their zoonotic importance more research is required to better understand the epidemiology, pathobiology and virulence determinants of these viruses and to develop improved control tools.

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Molecular analysis of avian H7 influenza viruses circulating in Eurasia in 1999–2005: detection of multiple reassortant virus genotypes

Journal of General Virology ◽

10.1099/vir.0.83111-0 ◽

2008 ◽

Vol 89 (1) ◽

pp. 48-59 ◽

Cited By ~ 41

Author(s):

Laura Campitelli ◽

Angela Di Martino ◽

Domenico Spagnolo ◽

Gavin J. D. Smith ◽

Livia Di Trani ◽

...

Keyword(s):

Avian Influenza ◽

Southern China ◽

Influenza Viruses ◽

Avian Influenza Viruses ◽

Phylogenetic Groups ◽

Entire Genome ◽

Domestic Poultry ◽

Virus Genotypes ◽

In The Wild ◽

Human Infections

Avian influenza infections by high and low pathogenicity H7 influenza viruses have caused several outbreaks in European poultry in recent years, also resulting in human infections. Although in some cases the source of H7 strains from domestic poultry was shown to be the viruses circulating in the wild bird reservoir, a thorough characterization of the entire genome of H7 viruses from both wild and domestic Eurasian birds, and their evolutionary relationships, has not been conducted. In our study, we have analysed low pathogenicity H7 influenza strains isolated from wild and domestic ducks in Italy and southern China and compared them with those from reared terrestrial poultry such as chicken and turkey. Phylogenetic analysis demonstrated that the H7 haemagglutinin genes were all closely related to each other, whereas the remaining genes could be divided into two or more phylogenetic groups. Almost each year different H7 reassortant viruses were identified and in at least two different years more than one H7 genotype co-circulated. A recent precursor in wild waterfowl was identified for most of the gene segments of terrestrial poultry viruses. Our data suggest that reassortment allows avian influenza viruses, in their natural reservoir, to increase their genetic diversity. In turn this might help avian influenza viruses colonize a wider range of hosts, including domestic poultry.

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Comparative Virological and Pathogenic Characteristics of Avian Influenza H5N8 Viruses Detected in Wild Birds and Domestic Poultry in Egypt during the Winter of 2016/2017

Viruses ◽

10.3390/v11110990 ◽

2019 ◽

Vol 11 (11) ◽

pp. 990 ◽

Cited By ~ 1

Author(s):

Yassmin Moatasim ◽

Ahmed Kandeil ◽

Basma Emad Aboulhoda ◽

Rabeh El-Shesheny ◽

Maha Alkhazindar ◽

...

Keyword(s):

Avian Influenza ◽

A549 Cells ◽

Wild Birds ◽

Influenza Viruses ◽

Multiple Introductions ◽

Domestic Poultry ◽

Growth Properties ◽

Reassortant Viruses

The surveillance and virological characterization of H5N8 avian influenza viruses are important in order to assess their zoonotic potential. The genetic analyses of the Egyptian H5N8 viruses isolated through active surveillance in wild birds and domestic poultry in the winter of 2016/2017 showed multiple introductions of reassortant viruses. In this study, we investigated and compared the growth kinetics, infectivity, and pathogenicity of the three reassortant forms of H5N8 viruses detected in wild birds and domestic poultry in Egypt during the first introduction wave in the winter of 2016/2017. Three representative H5N8 viruses (abbreviated as 813, 871, and 13666) were selected. The 871/H5N8 virus showed enhanced growth properties in vitro in Madin Darby canine kidney (MDCK) and A549 cells. Interestingly, all viruses replicated well in mice without prior adaptation. Infected C57BL/6 mice showed 20% mortality for 813/H5N8 and 60% mortality for 871/H5N8 and 13666/H5N8, which could be attributed to the genetic differences among the viruses. Studies on the pathogenicity in experimentally infected ducks revealed a range of pathogenic effects, with mortality rate ranging from 0% for 813/H5N8 and 13666/H5N8 to 28% for 871/H5N8. No significant differences were observed among the three compared viruses in infected chickens. Overall, different H5N8 viruses had variable biological characteristics, indicating a continuous need for surveillance and virus characterization efforts.

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Genetic analyses of avian influenza viruses in Mongolia, 2007 to 2009, and their relationships with Korean isolates from domestic poultry and wild birds

Poultry Science ◽

10.3382/ps.2011-01524 ◽

2011 ◽

Vol 90 (10) ◽

pp. 2229-2242 ◽

Cited By ~ 11

Author(s):

H.-M. Kang ◽

M.-C. Kim ◽

J.-G. Choi ◽

D. Batchuluun ◽

T.-O. Erdene-Ochir ◽

...

Keyword(s):

Avian Influenza ◽

Wild Birds ◽

Influenza Viruses ◽

Avian Influenza Viruses ◽

Genetic Analyses ◽

Domestic Poultry

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Dominant subtype switch in avian influenza viruses during 2016–2019 in China

Nature Communications ◽

10.1038/s41467-020-19671-3 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Yuhai Bi ◽

Juan Li ◽

Shanqin Li ◽

Guanghua Fu ◽

Tao Jin ◽

...

Keyword(s):

Avian Influenza ◽

Influenza Viruses ◽

Increased Risk ◽

Live Poultry ◽

Almost All ◽

Human Infections ◽

And Control ◽

Avian Populations ◽

Generation Sequencing ◽

Live Poultry Markets

AbstractWe have surveyed avian influenza virus (AIV) genomes from live poultry markets within China since 2014. Here we present a total of 16,091 samples that were collected from May 2016 to February 2019 in 23 provinces and municipalities in China. We identify 2048 AIV-positive samples and perform next generation sequencing. AIV-positive rates (12.73%) from samples had decreased substantially since 2016, compared to that during 2014–2016 (26.90%). Additionally, H9N2 has replaced H5N6 and H7N9 as the dominant AIV subtype in both chickens and ducks. Notably, novel reassortants and variants continually emerged and disseminated in avian populations, including H7N3, H9N9, H9N6 and H5N6 variants. Importantly, almost all of the H9 AIVs and many H7N9 and H6N2 strains prefer human-type receptors, posing an increased risk for human infections. In summary, our nation-wide surveillance highlights substantial changes in the circulation of AIVs since 2016, which greatly impacts the prevention and control of AIVs in China and worldwide.

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Genetic Characteristics of Avian Influenza Virus Isolated from Wild Birds in South Korea, 2019–2020

Viruses ◽

10.3390/v13030381 ◽

2021 ◽

Vol 13 (3) ◽

pp. 381

Author(s):

Eun-Jee Na ◽

Young-Sik Kim ◽

Sook-Young Lee ◽

Yoon-Ji Kim ◽

Jun-Soo Park ◽

...

Keyword(s):

Avian Influenza ◽

South Korea ◽

Basic Amino Acid ◽

Histopathological Change ◽

Amino Acid Sequences ◽

Wild Birds ◽

Influenza Viruses ◽

Economic Losses ◽

Active Monitoring ◽

Genetic Characteristics

Wild aquatic birds, a natural reservoir of avian influenza viruses (AIVs), transmit AIVs to poultry farms, causing huge economic losses. Therefore, the prevalence and genetic characteristics of AIVs isolated from wild birds in South Korea from October 2019 to March 2020 were investigated and analyzed. Fresh avian fecal samples (3256) were collected by active monitoring of 11 wild bird habitats. Twenty-eight AIVs were isolated. Seven HA and eight NA subtypes were identified. All AIV hosts were Anseriformes species. The HA cleavage site of 20 representative AIVs was encoded by non-multi-basic amino acid sequences. Phylogenetic analysis of the eight segment genes of the AIVs showed that most genes clustered within the Eurasian lineage. However, the HA gene of H10 viruses and NS gene of four viruses clustered within the American lineage, indicating intercontinental reassortment of AIVs. Representative viruses likely to infect mammals were selected and evaluated for pathogenicity in mice. JB21-58 (H5N3), JB42-93 (H9N2), and JB32-81 (H11N2) were isolated from the lungs, but JB31-69 (H11N9) was not isolated from the lungs until the end of the experiment at 14 dpi. None of infected mice showed clinical sign and histopathological change in the lung. In addition, viral antigens were not detected in lungs of all mice at 14 dpi. These data suggest that LPAIVs derived from wild birds are unlikely to be transmitted to mammals. However, because LPAIVs can reportedly infect mammals, including humans, continuous surveillance and monitoring of AIVs are necessary, despite their low pathogenicity.

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

Viruses ◽

10.3390/v13020212 ◽

2021 ◽

Vol 13 (2) ◽

pp. 212

Author(s):

Josanne H. Verhagen ◽

Ron A. M. Fouchier ◽

Nicola Lewis

Keyword(s):

Avian Influenza ◽

Highly Pathogenic Avian Influenza ◽

Wild Birds ◽

Influenza Viruses ◽

Highly Pathogenic ◽

Future Directions ◽

Pathogenic Avian Influenza ◽

Domestic Bird ◽

Hpai H5n1 ◽

Host Identification

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.

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Antibody responses to avian influenza viruses in wild birds broaden with age

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.2159 ◽

2016 ◽

Vol 283 (1845) ◽

pp. 20162159 ◽

Cited By ~ 11

Author(s):

Sarah C. Hill ◽

Ruth J. Manvell ◽

Bodo Schulenburg ◽

Wendy Shell ◽

Paul S. Wikramaratna ◽

...

Keyword(s):

Avian Influenza ◽

Haemagglutination Inhibition ◽

Wild Birds ◽

Influenza Viruses ◽

Antibody Responses ◽

Immune Recognition ◽

Avian Influenza Viruses ◽

Highly Pathogenic ◽

Age Related ◽

Pathogenic H5n1

For viruses such as avian influenza, immunity within a host population can drive the emergence of new strains by selecting for viruses with novel antigens that avoid immune recognition. The accumulation of acquired immunity with age is hypothesized to affect how influenza viruses emerge and spread in species of different lifespans. Despite its importance for understanding the behaviour of avian influenza viruses, little is known about age-related accumulation of immunity in the virus's primary reservoir, wild birds. To address this, we studied the age structure of immune responses to avian influenza virus in a wild swan population ( Cygnus olor ), before and after the population experienced an outbreak of highly pathogenic H5N1 avian influenza in 2008. We performed haemagglutination inhibition assays on sampled sera for five avian influenza strains and show that breadth of response accumulates with age. The observed age-related distribution of antibody responses to avian influenza strains may explain the age-dependent mortality observed during the highly pathogenic H5N1 outbreak. Age structures and species lifespan are probably important determinants of viral epidemiology and virulence in birds.

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Detection of low pathogenic avian influenza viruses in wild birds in Castilla-La Mancha (south central Spain)

Veterinary Microbiology ◽

10.1016/j.vetmic.2010.05.008 ◽

2010 ◽

Vol 146 (3-4) ◽

pp. 200-208 ◽

Cited By ~ 29

Author(s):

Elisa Pérez-Ramírez ◽

Xeider Gerrikagoitia ◽

Marta Barral ◽

Ursula Höfle

Keyword(s):

Avian Influenza ◽

Wild Birds ◽

Influenza Viruses ◽

Avian Influenza Viruses ◽

Central Spain ◽

Pathogenic Avian Influenza ◽

South Central ◽

La Mancha ◽

Low Pathogenic Avian Influenza

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Novel Highly Pathogenic Avian A(H5N2) and A(H5N8) Influenza Viruses of Clade 2.3.4.4 from North America Have Limited Capacity for Replication and Transmission in Mammals

mSphere ◽

10.1128/msphere.00003-16 ◽

2016 ◽

Vol 1 (2) ◽

Cited By ~ 37

Author(s):

Bryan S. Kaplan ◽

Marion Russier ◽

Trushar Jeevan ◽

Bindumadhav Marathe ◽

Elena A. Govorkova ◽

...

Keyword(s):

North America ◽

Avian Influenza ◽

North American ◽

Influenza Viruses ◽

Morbidity And Mortality ◽

Avian Influenza Viruses ◽

Highly Pathogenic ◽

The North ◽

Domestic Poultry ◽

The Impact

ABSTRACT Highly pathogenic H5 influenza viruses have been introduced into North America from Asia, causing extensive morbidity and mortality in domestic poultry. The introduced viruses have reassorted with North American avian influenza viruses, generating viral genotypes not seen on other continents. The experiments and analyses presented here were designed to assess the impact of this genetic diversification on viral phenotypes, particularly as regards mammalian hosts, by comparing the North American viruses with their Eurasian precursor viruses. Highly pathogenic influenza A(H5N8) viruses from clade 2.3.4.4 were introduced to North America by migratory birds in the fall of 2014. Reassortment of A(H5N8) viruses with avian viruses of North American lineage resulted in the generation of novel A(H5N2) viruses with novel genotypes. Through sequencing of recent avian influenza viruses, we identified PB1 and NP gene segments very similar to those in the viruses isolated from North American waterfowl prior to the introduction of A(H5N8) to North America, highlighting these bird species in the origin of reassortant A(H5N2) viruses. While they were highly virulent and transmissible in poultry, we found A(H5N2) viruses to be low pathogenic in mice and ferrets, and replication was limited in both hosts compared with those of recent highly pathogenic avian influenza (HPAI) H5N1 viruses. Molecular characterization of the hemagglutinin protein from A(H5N2) viruses showed that the receptor binding preference, cleavage, and pH of activation were highly adapted for replication in avian species and similar to those of other 2.3.4.4 viruses. In addition, North American and Eurasian clade 2.3.4.4 H5NX viruses replicated to significantly lower titers in differentiated normal human bronchial epithelial cells than did seasonal human A(H1N1) and highly pathogenic A(H5N1) viruses isolated from a human case. Thus, despite their having a high impact on poultry, our findings suggest that the recently emerging North American A(H5N2) viruses are not expected to pose a substantial threat to humans and other mammals without further reassortment and/or adaptation and that reassortment with North American viruses has not had a major impact on viral phenotype. IMPORTANCE Highly pathogenic H5 influenza viruses have been introduced into North America from Asia, causing extensive morbidity and mortality in domestic poultry. The introduced viruses have reassorted with North American avian influenza viruses, generating viral genotypes not seen on other continents. The experiments and analyses presented here were designed to assess the impact of this genetic diversification on viral phenotypes, particularly as regards mammalian hosts, by comparing the North American viruses with their Eurasian precursor viruses.

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