Properties and Dissemination of H5N1 Viruses Isolated During an Influenza Outbreak in Migratory Waterfowl in Western China

Harbin Veterinary Research Institute, Harbin 150001, People's Republic of China.
Journal of Virology (Impact Factor: 4.44). 07/2006; 80(12):5976-83. DOI: 10.1128/JVI.00110-06
Source: PubMed


H5N1 influenza A viruses are widely distributed among poultry in Asia, but until recently, only a limited number of wild birds were affected. During late April through June 2005, an outbreak of H5N1 virus infection occurred among wild birds at Qinghai Lake in China. Here, we describe the features of this outbreak. First identified in bar-headed geese, the disease soon spread to other avian species populating the lake. Sequence analysis of 15 viruses representing six avian species and collected at different times during the outbreak revealed four different H5N1 genotypes. Most of the isolates possessed lysine at position 627 in the PB2 protein, a residue known to be associated with virulence in mice and adaptation to humans. However, neither of the two index viruses possessed this residue. All of the viruses tested were pathogenic in mice, with the exception of one index virus. We also tested the replication of two viruses isolated during the Qinghai Lake outbreak and one unrelated duck H5N1 virus in rhesus macaques. The Qinghai Lake viruses did not replicate efficiently in these animals, producing no evidence of disease other than transient fever, while the duck virus replicated in multiple organs and caused symptoms of respiratory illness. Importantly, H5N1 viruses isolated in Mongolia, Russia, Inner Mongolia, and the Liaoning Province of China after August 2005 were genetically closely related to one of the genotypes isolated during the Qinghai outbreak, suggesting the dominant nature of this genotype and underscoring the need for worldwide intensive surveillance to minimize its devastating consequences.

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Available from: Yanbing Li, Nov 11, 2014
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    • ", the first mass outbreak of HPAI H5N1 in wild birds was reported in Qinghai Lake, China – a significant stopover site within the Central Asian Flyway (Chen et al., 2006a). In July 2005, the same H5N1 virus isolated in Qinghai was reported in dead migratory birds in Russia, the first country to report H5N1 outside Asia (World Health Organization, 2011). "
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    ABSTRACT: The aim of this work was to explore the comparative epidemiology of influenza viruses, H5N1 and H7N9, in both bird and human populations. Specifically, the article examines similarities and differences between the two viruses in their genetic characteristics, distribution patterns in human and bird populations and postulated mechanisms of global spread. In summary, H5N1 is pathogenic in birds, while H7N9 is not. Yet both have caused sporadic human cases, without evidence of sustained, human-to-human spread. The number of H7N9 human cases in the first year following its emergence far exceeded that of H5N1 over the same time frame. Despite the higher incidence of H7N9, the spatial distribution of H5N1 within a comparable time frame is considerably greater than that of H7N9, both within China and globally. The pattern of spread of H5N1 in humans and birds around the world is consistent with spread through wild bird migration and poultry trade activities. In contrast, human cases of H7N9 and isolations of H7N9 in birds and the environment have largely occurred in a number of contiguous provinces in south-eastern China. Although rates of contact with birds appear to be similar in H5N1 and H7N9 cases, there is a predominance of incidental contact reported for H7N9 as opposed to close, high-risk contact for H5N1. Despite the high number of human cases of H7N9 and the assumed transmission being from birds, the corresponding level of H7N9 virus in birds in surveillance studies has been low, particularly in poultry farms. H7N9 viruses are also diversifying at a much greater rate than H5N1 viruses. Analyses of certain H7N9 strains demonstrate similarities with engineered transmissible H5N1 viruses which make it more adaptable to the human respiratory tract. These differences in the human and bird epidemiology of H5N1 and H7N9 raise unanswered questions as to how H7N9 has spread, which should be investigated further.
    Full-text · Article · Jan 2015 · Transboundary and Emerging Diseases
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    • "This may also be attributed to co-infection with other pathogens, bad hygiene and/or stress of flying. Thus, our study further indicates that H5N1 HPAIVs have established infection and pathogenicity among various aquatic and wild birds, suggesting that the viruses are continuously evolving compared with previously endemic HPAIVs (Ellis et al., 2004; Chen et al., 2006). "
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    ABSTRACT: The highly pathogenic avian influenza virus (HPAIV) subtype H5N1 threatens animal and human health worldwide. Susceptibility of pigeons to HPAIV (H5N1) and their role in AIV transmission to domestic birds and humans remain questionable. In this study, an outbreak in domestic pigeons (1-18 months old) with 50% mortality was investigated. Pigeons exhibited nervous manifestations and greenish diarrhea. Necropsy of the naturally infected pigeons revealed congestion of the internal organs, particularly lungs and brain. A HPAIV subtype H5N1 designated A/Pigeon/Egypt/SHAH-5803/2011 was isolated from 40 days old pigeon. Sequencing of the hemagglutinin gene showed close relation to viruses in group 2.2.1/C. Intravenous inoculation of the isolate in chickens induced 100% mortality within 2 days postinoculation (dpi) and intravenous pathogenicity index was 2.7. Virus pathogenicity and transmissibility was determined experimentally in six-week-old domestic pigeons. Thirty percent of pigeons inoculated oronasally with 10(6) EID50 showed congested beak, conjunctivitis, depression and greenish diarrhea. A mortality rate of 10% was recorded preceded by severe neurologic signs consisting of torticollis, incoordination, tremors, and wing paralysis. Pathological examination revealed a friable brain tissue and congested meningeal blood vessels. The lungs appeared edematous and severely hemorrhagic. Subepicardial and petechial hemorrhages on the coronary fat were observed. Both infected and contact pigeons shed virus via the oropharynx and cloaca. To our knowledge, this is the first description and characterization of HPAIV in naturally infected pigeons in Egypt. Our findings reveal that pigeons can indeed be susceptible to H5N1 HPAI viruses and could be a source of infection to other birds and human.
    Full-text · Article · May 2014 · Avian Pathology
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    • "While these infections do not cause significant disease among wild birds, there is some evidence of subclinical signs of low pathogenic (LP) AIV infection in free living waterfowl [1], [2]. Historically, highly pathogenic (HP) AIVs have rarely been seen in wild birds, but since 1997 when HPAIV H5N1 began circulating among domestic waterfowl and terrestrial birds primarily in southeast Asia, mortality events affecting wild birds due to this disease have been extensively documented [3], [4]. This raised the question of whether wild migratory birds facilitated the spread of HPAIV H5N1 throughout Asia, Africa and Europe and whether they will be the mechanism for introduction of this virus, or future HPAIV, into the Americas [5]. "
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    ABSTRACT: Avian influenza virus (AIV) in wild birds has been of increasing interest over the last decade due to the emergence of AIVs that cause significant disease and mortality in both poultry and humans. While research clearly demonstrates that AIVs can move across the Pacific or Atlantic Ocean, there has been no data to support the mechanism of how this occurs. In spring and autumn of 2010 and autumn of 2011 we obtained cloacal swab samples from 1078 waterfowl, gulls, and shorebirds of various species in southwest and west Iceland and tested them for AIV. From these, we isolated and fully sequenced the genomes of 29 AIVs from wild caught gulls (Charadriiformes) and waterfowl (Anseriformes) in Iceland. We detected viruses that were entirely (8 of 8 genomic segments) of American lineage, viruses that were entirely of Eurasian lineage, and viruses with mixed American-Eurasian lineage. Prior to this work only 2 AIVs had been reported from wild birds in Iceland and only the sequence from one segment was available in GenBank. This is the first report of finding AIVs of entirely American lineage and Eurasian lineage, as well as reassortant viruses, together in the same geographic location. Our study demonstrates the importance of the North Atlantic as a corridor for the movement of AIVs between Europe and North America.
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