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He J, Kam YW. Insights from Avian Influenza: A Review of Its Multifaceted Nature and Future Pandemic Preparedness. Viruses 2024; 16:458. [PMID: 38543823 PMCID: PMC10975894 DOI: 10.3390/v16030458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/14/2024] [Accepted: 03/15/2024] [Indexed: 05/23/2024] Open
Abstract
Avian influenza viruses (AIVs) have posed a significant pandemic threat since their discovery. This review mainly focuses on the epidemiology, virology, pathogenesis, and treatments of avian influenza viruses. We delve into the global spread, past pandemics, clinical symptoms, severity, and immune response related to AIVs. The review also discusses various control measures, including antiviral drugs, vaccines, and potential future directions in influenza treatment and prevention. Lastly, by summarizing the insights from previous pandemic control, this review aims to direct effective strategies for managing future influenza pandemics.
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Affiliation(s)
| | - Yiu-Wing Kam
- Division of Natural and Applied Science, Duke Kunshan University, No. 8 Duke Avenue, Kunshan 215316, China;
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Zanin M, Le TB, Na W, Kang JA, Kwon HJ, Hwang J, Ga EH, Wong SS, Cho HJ, Song D, Kim HK, Jeong DG, Yoon SW. Potential for transmission of naturally mutated H10N1 avian influenza virus to mammalian hosts and causing severe pulmonary disease. Front Microbiol 2023; 14:1256090. [PMID: 37779710 PMCID: PMC10536253 DOI: 10.3389/fmicb.2023.1256090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 08/21/2023] [Indexed: 10/03/2023] Open
Abstract
Subtype H10 avian influenza viruses (AIV) are distributed worldwide in wild aquatic birds, and can infect humans and several other mammalian species. In the present study, we investigated the naturally mutated PB2 gene in A/aquatic bird/South Korea/SW1/2018 (A/SW1/18, H10N1), isolated from wild birds during the 2018-2019 winter season. This virus was originally found in South Korea, and is similar to isolates from mainland China and Mongolia. It had low pathogenicity, lacked a multi-basic cleavage site, and showed a binding preference for α2,3-linked sialic acids. However, it can infect mice, causing severe disease and lung pathology. SW1 was also transmitted by direct contact in ferrets, and replicated in the respiratory tract tissue, with no evidence of extrapulmonary spread. The pathogenicity and transmissibility of SW1 in mouse and ferret models were similar to those of the pandemic strain A/California/04/2009 (A/CA/04, H1N1). These factors suggest that subtype H10 AIVs have zoonotic potential and may transmit from human to human, thereby posing a potential threat to public health. Therefore, the study highlights the urgent need for closer monitoring of subtype H10 AIVs through continued surveillance of wild aquatic birds.
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Affiliation(s)
- Mark Zanin
- School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Tran Bac Le
- Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea
| | - Woonsung Na
- College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
| | - Jung-Ah Kang
- Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea
| | - Hyung-Jun Kwon
- College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
| | - Jaehyun Hwang
- College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
| | - Eul Hae Ga
- College of Veterinary Medicine, Chonnam National University, Gwangju, Republic of Korea
| | - Sook-San Wong
- School of Public Health, The University of Hong Kong, Hong Kong, Hong Kong SAR, China
| | - Hae-Jin Cho
- Korea Institute of Environment Ecology, Daejeon, Republic of Korea
| | - Daesub Song
- College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea
| | - Hye Kwon Kim
- Department of Microbiology, College of Natural Sciences, Chungbuk National University, Cheongju, Republic of Korea
| | - Dae Gwin Jeong
- Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea
| | - Sun-Woo Yoon
- Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea
- Department of Vaccine Biotechnology, College of Life Sciences and Health Welfare, Andong National University, Andong, Republic of Korea
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Xie R, Wang W, Gao Y, Liu W, Yue B, Liu S, Fan W, Song S, Yan L. Evolution and mammalian adaptation of H3 and H10 subtype avian influenza viruses in wild birds in Yancheng Wetland of China. Vet Microbiol 2023; 279:109669. [PMID: 36724731 DOI: 10.1016/j.vetmic.2023.109669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/19/2023] [Accepted: 01/22/2023] [Indexed: 01/24/2023]
Abstract
Wild birds play a critical role in avian influenza virus (AIV) ecology and some outbreaks of avian influenza in human originate from wild birds, suggesting that epidemiological surveillance and interspecies-transmission analysis of AIVs in wild birds are critical. Since 2019, we have performed sampling in Yancheng Wetland along the East Asian-Australasian Flyway. Totally, 2054 fecal swabs were collected and one H3N8, two H3N1, one H10N8, and three H10N1 were isolated. Three H3 gene of AIVs we isolated belonged to Eurasian lineage, but the four H10 gene clustered into North American lineage. What's more, the H3 and the foreign H10 gene had generated novel reassortants in Yancheng wetland. Receptor binding assay indicated that nearly all strains, except D369/H10N1, presented a dual receptor-binding profile and bound to avian-type receptor preferentially. In animal experiment, all isolates could infect mice without prior adaptation and induce histopathological changes in mice lungs, moreover, all H3 subtype AIVs obviously triggered weight loss of mice. In addition to lung and turbinate, D322/H3N1, D338/H3N8, D211/H10N8 and D266/H10N1 could spread to brain and kidney or liver or spleen, showing a wider range of tissue tropism. Multiple mutants associated with mammalian adaptation were also detected in all isolates according to molecular analysis. These findings revealed that H3 and H10 AIVs circulating in wild birds in Yancheng Wetland underwent complex reassortment and increased mammalian adaptation, which highlighted the necessity to monitor the diverse reassortment of AIVs in wild birds and evaluate the risks of H3 and H10 viruses to human health.
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Affiliation(s)
- Ran Xie
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Wenjie Wang
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Yuan Gao
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Wenjian Liu
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Bin Yue
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Shuhui Liu
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Wentao Fan
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Suquan Song
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China
| | - Liping Yan
- MOE Joint International Research Laboratory of Animal Health and Food Safety, Jiangsu Detection Center of Terrestrial Wildlife Disease, Institute of Immunology and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China.
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Berry I, Rahman M, Flora MS, Greer AL, Morris SK, Khan IA, Sarkar S, Naureen T, Fisman DN, Mangtani P. Frequency and patterns of exposure to live poultry and the potential risk of avian influenza transmission to humans in urban Bangladesh. Sci Rep 2021; 11:21880. [PMID: 34750452 PMCID: PMC8575886 DOI: 10.1038/s41598-021-01327-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 10/26/2021] [Indexed: 11/18/2022] Open
Abstract
Avian influenza is endemic in Bangladesh, where greater than 90% of poultry are marketed through live poultry markets (LPMs). We conducted a population-based cross-sectional mobile telephone survey in urban Dhaka, Bangladesh to investigate the frequency and patterns of human exposure to live poultry in LPMs and at home. Among 1047 urban residents surveyed, 74.2% (95% CI 70.9-77.2) reported exposure to live poultry in the past year, with the majority of exposure occurring on a weekly basis. While visiting LPMs was less common amongst females (40.3%, 95% CI 35.0-45.8) than males (58.9%, 95% CI 54.0-63.5), females reported greater poultry exposure through food preparation, including defeathering (13.2%, 95% CI 9.5-17.9) and eviscerating (14.8%, 95% CI 11.2-19.4) (p < 0.001). A large proportion of the urban population is frequently exposed to live poultry in a setting where avian influenza viruses are endemic in LPMs. There is thus not only ample opportunity for spillover of avian influenza infections into humans in Dhaka, Bangladesh, but also greater potential for viral reassortment which could generate novel strains with pandemic potential.
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Affiliation(s)
- Isha Berry
- Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, ON, M5T 3M7, Canada.
| | - Mahbubur Rahman
- Institute of Epidemiology, Disease Control and Research, Dhaka, Bangladesh
| | | | - Amy L Greer
- Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, ON, M5T 3M7, Canada
- Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Shaun K Morris
- Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, ON, M5T 3M7, Canada
- Division of Infectious Disease and Center for Global Child Health, The Hospital for Sick Children, Toronto, ON, Canada
| | - Iqbal Ansary Khan
- Institute of Epidemiology, Disease Control and Research, Dhaka, Bangladesh
| | - Sudipta Sarkar
- Institute of Epidemiology, Disease Control and Research, Dhaka, Bangladesh
| | - Tanzila Naureen
- Institute of Epidemiology, Disease Control and Research, Dhaka, Bangladesh
| | - David N Fisman
- Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, ON, M5T 3M7, Canada
| | - Punam Mangtani
- London School of Hygiene and Tropical Medicine, London, UK
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Abstract
Avian influenza viruses pose a continuous threat to both poultry and human health, with significant economic impact. The ability of viruses to reassort and jump the species barrier into mammalian hosts generates a constant pandemic threat. H10Nx avian viruses have been shown to replicate in mammalian species without prior adaptation and have caused significant human infection and fatalities. They are able to rapidly reassort with circulating poultry strains and go undetected due to their low pathogenicity in chickens. Novel detections of both human reassortant strains and increasing endemicity of H10Nx poultry infections highlight the increasing need for heightened surveillance and greater understanding of the distribution, tropism, and infection capabilities of these viruses. In this minireview, we highlight the gap in the current understanding of this subtype and its prevalence across a vast range of host species and geographical locations.
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Liu K, Ding P, Pei Y, Gao R, Han W, Zheng H, Ji Z, Cai M, Gu J, Li X, Gu M, Hu J, Liu X, Hu S, Zhang P, Wang X, Wang X, Liu X. Emergence of a novel reassortant avian influenza virus (H10N3) in Eastern China with high pathogenicity and respiratory droplet transmissibility to mammals. SCIENCE CHINA-LIFE SCIENCES 2021; 65:1024-1035. [PMID: 34542812 DOI: 10.1007/s11427-020-1981-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 07/13/2021] [Indexed: 11/29/2022]
Abstract
Decades have passed since the first discovery of H10-subtype avian influenza virus (AIV) in chickens in 1949, and it has been detected in many species including mammals such as minks, pigs, seals and humans. Cases of human infections with H10N8 viruses identified in China in 2013 have raised widespread attention. Two novel reassortant H10N3 viruses were isolated from chickens in December 2019 in eastern China during routine surveillance for AIVs. The internal genes of these viruses were derived from genotype S (G57) H9N2 and were consistent with H5N6, H7N9 and H10N8, which cause fatal infections in humans. Their viral pathogenicity and transmissibility were further studied in different animal models. The two H10N3 isolates had low pathogenicity in chickens and were transmitted between chickens via direct contact. These viruses were highly pathogenic in mice and could be transmitted between guinea pigs via direct contact and respiratory droplets. More importantly, these viruses can bind to both human-type SAα-2,6-Gal receptors and avian-type SAα-2,3-Gal receptors. Asymptomatic shedding in chickens and good adaptability to mammals of these H10N3 isolates would make it easier to transmit to humans and pose a threat to public health.
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Affiliation(s)
- Kaituo Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Pingyun Ding
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Yuru Pei
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Ruyi Gao
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China
| | - Wenwen Han
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Huafen Zheng
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Zhuxing Ji
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Miao Cai
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Jinyuan Gu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Xiuli Li
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Min Gu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China
| | - Jiao Hu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China
| | - Xiaowen Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China
| | - Shunlin Hu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China
| | - Pinghu Zhang
- Institute of Translational Medicine, Key Laboratory of Geriatric Disease Prevention and Control of Jiangsu Province, Medical College, Yangzhou University, Yangzhou, 225009, China
| | - Xiaobo Wang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China
| | - Xiaoquan Wang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China. .,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China.
| | - Xiufan Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China. .,Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China.
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Will A, Thiebot JB, Ip HS, Shoogukwruk P, Annogiyuk M, Takahashi A, Shearn-Bochsler V, Killian ML, Torchetti M, Kitaysky A. Investigation of the 2018 thick-billed murre ( Uria lomvia) die-off on St. Lawrence Island rules out food shortage as the cause. DEEP-SEA RESEARCH. PART II, TOPICAL STUDIES IN OCEANOGRAPHY 2020; 181-182:104879. [PMID: 33716412 PMCID: PMC7949294 DOI: 10.1016/j.dsr2.2020.104879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Die-offs of seabirds in Alaska have occurred with increased frequency since 2015. In 2018, on St. Lawrence Island, seabirds were reported washing up dead on beaches starting in late May, peaking in June, and continuing until early August. The cause of death was documented to be starvation, leading to the conclusion that a severe food shortage was to blame. We use physiology and colony-based observations to examine whether food shortage is a sufficient explanation for the die-off, or if evidence indicates an alternative cause of starvation such as disease. Specifically, we address what species were most affected, the timing of possible food shortages, and food shortage severity in a historical context. We found that thick-billed murres (Uria lomvia) were most affected by the die-off, making up 61% of all bird carcasses encountered during beach surveys. Thick-billed murre carcasses were proportionately more numerous (26:1) than would be expected based on ratios of thick-billed murres to co-occurring common murres (U. aalge) observed on breeding study plots (7:1). Concentrations of the stress hormone corticosterone, a reliable physiological indicator of nutritional stress, in thick-billed murre feathers grown in the fall indicate that foraging conditions in the northern Bering Sea were poor in the fall of 2017 and comparable in severity to those experienced by murres during the 1976-1977 Bering Sea regime shift. Concentrations of corticosterone in feathers grown during the pre-breeding molt indicate that foraging conditions in late winter 2018 were similar to previous years. The 2018 murre egg harvest in the village of Savoonga (on St. Lawrence Is.) was one-fifth the 1993-2012 average, and residents observed that fewer birds laid eggs in 2018. Exposure of thick-billed murres to nutritional stress in August, however, was no different in 2018 compared to 2016, 2017, and 2019, and was comparable to levels observed on St. George Island in 2003-2017. Prey abundance, measured by the National Oceanic and Atmospheric Administration in bottom-trawl surveys, was also similar in 2018 to 2017 and 2019, supporting the evidence that food was not scarce in the summer of 2018 in the vicinity of St. Lawrence Island. Of two moribund thick-billed murres collected at the end of the mortality event, one tested positive for a novel re-assortment H10 strain of avian influenza with Eurasian components, likely contracted during the non-breeding season. It is not currently known how widely spread infection of murres with the novel virus was, thus insufficient evidence exists to attribute the die-off to an outbreak of avian influenza. We conclude that food shortage alone is not an adequate explanation for the mortality of thick-billed murres in 2018, and highlight the importance of rapid response to mortality events in order to document alternative or confounding causes of mortality.
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Affiliation(s)
- Alexis Will
- National Institute of Polar Research, Tokyo, Japan
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
- Corresponding author: (A. Will)
| | | | - Hon S. Ip
- U.S. Geological Survey, National Wildlife Health Center., Madison, Wisconsin
| | | | | | | | | | - Mary Lea Killian
- National Veterinary Services Laboratories, United States Department of Agriculture, Ames, Iowa
| | - Mia Torchetti
- National Veterinary Services Laboratories, United States Department of Agriculture, Ames, Iowa
| | - Alexander Kitaysky
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
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Continued Evolution of H5Nx Avian Influenza Viruses in Bangladeshi Live Poultry Markets: Pathogenic Potential in Poultry and Mammalian Models. J Virol 2020; 94:JVI.01141-20. [PMID: 32907981 DOI: 10.1128/jvi.01141-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Accepted: 08/21/2020] [Indexed: 11/20/2022] Open
Abstract
The genesis of novel influenza viruses through reassortment poses a continuing risk to public health. This is of particular concern in Bangladesh, where highly pathogenic avian influenza viruses of the A(H5N1) subtype are endemic and cocirculate with other influenza viruses. Active surveillance of avian influenza viruses in Bangladeshi live poultry markets detected three A(H5) genotypes, designated H5N1-R1, H5N1-R2, and H5N2-R3, that arose from reassortment of A(H5N1) clade 2.3.2.1a viruses. The H5N1-R1 and H5N1-R2 viruses contained HA, NA, and M genes from the A(H5N1) clade 2.3.2.1a viruses and PB2, PB1, PA, NP, and NS genes from other Eurasian influenza viruses. H5N2-R3 viruses contained the HA gene from circulating A(H5N1) clade 2.3.2.1a viruses, NA and M genes from concurrently circulating A(H9N2) influenza viruses, and PB2, PB1, PA, NP, and NS genes from other Eurasian influenza viruses. Representative viruses of all three genotypes and a parental clade 2.3.2.1a strain (H5N1-R0) infected and replicated in mice without prior adaptation; the H5N2-R3 virus replicated to the highest titers in the lung. All viruses efficiently infected and killed chickens. All viruses replicated in inoculated ferrets, but no airborne transmission was detected, and only H5N2-R3 showed limited direct-contact transmission. Our findings demonstrate that although the A(H5N1) viruses circulating in Bangladesh have the capacity to infect and replicate in mammals, they show very limited capacity for transmission. However, reassortment does generate viruses of distinct phenotypes.IMPORTANCE Highly pathogenic avian influenza A(H5N1) viruses have circulated continuously in Bangladesh since 2007, and active surveillance has detected viral evolution driven by mutation and reassortment. Recently, three genetically distinct A(H5N1) reassortant viruses were detected in live poultry markets in Bangladesh. Currently, we cannot assign pandemic risk by only sequencing viruses; it must be conducted empirically. We found that the H5Nx highly pathogenic avian influenza viruses exhibited high virulence in mice and chickens, and one virus had limited capacity to transmit between ferrets, a property considered consistent with a higher zoonotic risk.
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