scholarly journals Avian influenza viruses in humans: lessons from past outbreaks

2019 ◽  
Vol 132 (1) ◽  
pp. 81-95 ◽  
Author(s):  
Yao-Tsun Li ◽  
Martin Linster ◽  
Ian H Mendenhall ◽  
Yvonne C F Su ◽  
Gavin J D Smith
Keyword(s):  
Risk Factors ◽  
Avian Influenza ◽  
Virus Transmission ◽  
Human Infection ◽  
Influenza Viruses ◽  
Avian Species ◽  
Avian Influenza Viruses ◽  
Virus Surveillance ◽  
Changing Patterns ◽  
Human Infections

Abstract Background Human infections with avian influenza viruses (AIV) represent a persistent public health threat. The principal risk factor governing human infection with AIV is from direct contact with infected poultry and is primarily observed in Asia and Egypt where live-bird markets are common. Areas of agreement Changing patterns of virus transmission and a lack of obvious disease manifestations in avian species hampers early detection and efficient control of potentially zoonotic AIV. Areas of controversy Despite extensive studies on biological and environmental risk factors, the exact conditions required for cross-species transmission from avian species to humans remain largely unknown. Growing points The development of a universal (‘across-subtype’) influenza vaccine and effective antiviral therapeutics are a priority. Areas timely for developing research Sustained virus surveillance and collection of ecological and physiological parameters from birds in different environments is required to better understand influenza virus ecology and identify risk factors for human infection.

scholarly journals Zoonotic Potential of Currently Circulating Avian Influenza Viruses

2020 ◽  
Vol 39 (1) ◽  
pp. 8-14
Author(s):  
Vladimir Savić
Keyword(s):  
Avian Influenza ◽  
Influenza A ◽  
Human Infection ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Avian Influenza Viruses ◽  
Influenza Pandemics ◽  
Human Infections ◽  
Virus Adaptation ◽  
Efficient Transmission

Over the past and the current centuries, human influenza pandemics have been attributable to viruses with an avian ancestry. Birds are the main source of influenza A viruses and harbour a variety of antigenic subtypes. Certain avian influenza viruses are capable for cross-species transmission including human infections. Although sustained intrehuman transmission of such viruses has not been documented so far, each human infection with avian influenza viruses provides chances for the virus adaptation towards efficient transmission within human population. Here are reviewed currently circulating avian influenza viruses that are of major significance for public health.

scholarly journals Vaccination with Consensus H7 Elicits Broadly Reactive and Protective Antibodies against Eurasian and North American Lineage H7 Viruses

Vaccines ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 143
Author(s):  
Gendeal M. Fadlallah ◽  
Fuying Ma ◽  
Zherui Zhang ◽  
Mengchan Hao ◽  
Juefu Hu ◽  
...  
Keyword(s):  
Avian Influenza ◽  
North American ◽  
Human Infection ◽  
Influenza Viruses ◽  
Avian Influenza Viruses ◽  
Lethal Challenge ◽  
Protective Antibodies ◽  
H7 Subtype ◽  
H7n3 Virus

H7 subtype avian influenza viruses have caused outbreaks in poultry, and even human infection, for decades in both Eurasia and North America. Although effective vaccines offer the best protection against avian influenza viruses, antigenically distinct Eurasian and North American lineage subtype H7 viruses require the development of cross-protective vaccine candidates. In this study, a methodology called computationally optimized broadly reactive antigen (COBRA) was used to develop four consensus H7 antigens (CH7-22, CH7-24, CH7-26, and CH7-28). In vitro experiments confirmed the binding of monoclonal antibodies to the head and stem domains of cell surface-expressed consensus HAs, indicating display of their antigenicity. Immunization with DNA vaccines encoding the four antigens was evaluated in a mouse model. Broadly reactive antibodies against H7 viruses from Eurasian and North American lineages were elicited and detected by binding, inhibition, and neutralizing analyses. Further infection with Eurasian H7N9 and North American H7N3 virus strains confirmed that CH7-22 and CH7-24 conferred the most effective protection against hetero-lethal challenge. Our data showed that the consensus H7 vaccines elicit a broadly reactive, protective response against Eurasian and North American lineage H7 viruses, which are suitable for development against other zoonotic influenza viruses.

scholarly journals Development of a duplex TaqMan real-time RT-PCR assay for simultaneous detection of newly emerged H5N6 influenza viruses

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Lin Liu ◽  
Ying Zhang ◽  
Pengfei Cui ◽  
Congcong Wang ◽  
Xianying Zeng ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Avian Influenza ◽  
Simultaneous Detection ◽  
Reaction System ◽  
Taxonomic Status ◽  
Human Infection ◽  
Influenza Viruses ◽  
Rt Pcr ◽  
Avian Influenza Viruses ◽  
Pcr Assay

Abstract Background In 2017–2018, a new highly pathogenic H5N6 avian influenza virus (AIV) variant appeared in poultry and wild birds in Asian and European countries and caused multiple outbreaks. These variant strains are different from the H5N6 virus associated with human infection in previous years, and their genetic taxonomic status and antigenicity have changed. Therefore, revision of the primers and probes of fluorescent RT-PCR is important to detect the new H5N6 subtype AIV in poultry and reduce the risk of an epidemic in birds or humans. Methods In this study, the primers and probes including three groups of HA and four groups of NA for H5N6 influenza virus were evaluated. Then a set of ideal primer and probes were selected to further optimize the reaction system and established a method of double rRT-PCR assay. The specificity of this method was determined by using H1~H16 subtype AIV. Results The results showed that fluorescence signals were obtained for H5 virus in FAM channel and N6 virus in VIC channel, and no fluorescent signal was observed in other subtypes of avian influenza viruses. The detection limit of this assay was 69 copies for H5 and 83 copies for N6 gene. And, the variability tests of intra- and inter-assay showed excellent reproducibility. Moreover, this assay showed 100% agreement with virus isolation method in detecting samples from poultry. Conclusion The duplex rRT-PCR assay presented here has high specificity, sensitivity and reproducibility, and can be used for laboratory surveillance and rapid diagnosis of newly emerged H5N6 subtype avian influenza viruses.

scholarly journals Phenotypic Effects of Substitutions within the Receptor Binding Site of Highly Pathogenic Avian Influenza H5N1 Virus Observed during Human Infection

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
Dirk Eggink ◽  
Monique Spronken ◽  
Roosmarijn van der Woude ◽  
Jocynthe Buzink ◽  
Frederik Broszeit ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Binding Site ◽  
Receptor Binding ◽  
Human Infection ◽  
Influenza Viruses ◽  
Receptor Specificity ◽  
Receptor Binding Site ◽  
Human Type ◽  
Human Infections

ABSTRACT Highly pathogenic avian influenza (HPAI) viruses are enzootic in wild birds and poultry and continue to cause human infections with high mortality. To date, more than 850 confirmed human cases of H5N1 virus infection have been reported, of which ∼60% were fatal. Global concern persists that these or similar avian influenza viruses will evolve into viruses that can transmit efficiently between humans, causing a severe influenza pandemic. It was shown previously that a change in receptor specificity is a hallmark for adaptation to humans and evolution toward a transmittable virus. Substantial genetic diversity was detected within the receptor binding site of hemagglutinin of HPAI A/H5N1 viruses, evolved during human infection, as detected by next-generation sequencing. Here, we investigated the functional impact of substitutions that were detected during these human infections. Upon rescue of 21 mutant viruses, most substitutions in the receptor binding site (RBS) resulted in viable virus, but virus replication, entry, and stability were often impeded. None of the tested substitutions individually resulted in a clear switch in receptor preference as measured with modified red blood cells and glycan arrays. Although several combinations of the substitutions can lead to human-type receptor specificity, accumulation of multiple amino acid substitutions within a single hemagglutinin during human infection is rare, thus reducing the risk of virus adaptation to humans. IMPORTANCE H5 viruses continue to be a threat for public health. Because these viruses are immunologically novel to humans, they could spark a pandemic when adapted to transmit between humans. Avian influenza viruses need several adaptive mutations to bind to human-type receptors, increase hemagglutinin (HA) stability, and replicate in human cells. However, knowledge on adaptive mutations during human infections is limited. A previous study showed substantial diversity within the receptor binding site of H5N1 during human infection. We therefore analyzed the observed amino acid changes phenotypically in a diverse set of assays, including virus replication, stability, and receptor specificity. None of the tested substitutions resulted in a clear step toward a human-adapted virus capable of aerosol transmission. It is notable that acquiring human-type receptor specificity needs multiple amino acid mutations, and that variability at key position 226 is not tolerated, reducing the risk of them being acquired naturally.

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

2008 ◽  
Vol 89 (1) ◽  
pp. 48-59 ◽  
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.

scholarly journals Human infections with novel reassortant H5N6 avian influenza viruses in China

2017 ◽  
Vol 6 (1) ◽  
pp. 1-2 ◽  
Author(s):  
Ye Zhang ◽  
Minmei Chen ◽  
Yiwei Huang ◽  
Wenfei Zhu ◽  
Lei Yang ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Influenza Viruses ◽  
Avian Influenza Viruses ◽  
Human Infections

scholarly journals Serosurvey of Avian Influenza Viruses (H5, H7, and H9) and Associated Risk Factors in Backyard Poultry Flocks of Lahore District, Pakistan

2021 ◽  
Vol 8 ◽  
Author(s):  
Mamoona Chaudhry ◽  
Hamad Bin Rashid ◽  
Michael Thrusfield ◽  
Mark C. Eisler ◽  
Susan C. Welburn
Keyword(s):  
Risk Factors ◽  
Avian Influenza ◽  
Influenza Viruses ◽  
Flock Size ◽  
Avian Influenza Viruses ◽  
Cross Sectional Survey ◽  
Backyard Poultry ◽  
Associated Risk Factors ◽  
Backyard Birds ◽  
Different Sources

Rural poultry constitutes 56% of the total poultry population in Pakistan; however, epidemiological information about avian influenza viruses (AIVs) in backyard poultry flocks is lacking. A cross-sectional survey of villages of Lahore district was conducted from July 2009 to August 2009 using two-stage cluster sampling and probability proportional to size (PPS) sampling to estimate seroprevalence and its associated risk factors. A random selection of 35 clusters from 308 villages of Lahore were considered, and from each cluster, six chickens aged >2 months were selected. A total of 210 serum samples were collected and examined by the hemagglutination inhibition (HI) test for specific antibodies against AIV subtypes H5, H7, and H9. Overall weighted seroprevalence for AIVs was 65.2% (95% CI: 55.6–74.8%), and for subtype H5, H7 & H9 was 6.9% (95% CI: 10.8–23.0%), 0% (95% CI: 0–1.7%), and 62.0% (95% CI: 52.2–71.8%) respectively. However, none of the samples were positive for H7. The average flock size was 17.3 birds, and the main purpose of keeping poultry was for eggs/meat (70.6%, 95% CI: 59.7–81.4). A majority of them were reared in a semi-caged system (83%, 95% CI: 74.5–91.3). Backyard birds were received from different sources, that is, purchased from the market or received as a gift from friends or any NGO, and were 5.7 times more likely to become avian influenza (AI) seropositive than those that were not exposed to these sources (CI 95%: 2.0–716.0). Backyard birds which were received from different sources, that is, purchased from the market or received from friends or any NGO, were 5.7 times more likely to become AI seropositive compared to those that were not (CI 95%: 2.5–18.7). To reduce the risk of AIV in Pakistan, continuous surveillance of backyard poultry would be needed.

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