Rapid Emergence of Highly Pathogenic Avian Influenza Subtypes from a Subtype H5N1 Hemagglutinin Variant

Global mapping of highly pathogenic avian influenza H5N1 and H5Nx clade 2.3.4.4 viruses with spatial cross-validation

Global disease suitability models are essential tools to inform surveillance systems and enable early detection. We present the first global suitability model of highly pathogenic avian influenza (HPAI) H5N1 and demonstrate that reliable predictions can be obtained at global scale. Best predictions are obtained using spatial predictor variables describing host distributions, rather than land use or eco-climatic spatial predictor variables, with a strong association with domestic duck and extensively raised chicken densities. Our results also support a more systematic use of spatial cross-validation in large-scale disease suitability modelling compared to standard random cross-validation that can lead to unreliable measure of extrapolation accuracy. A global suitability model of the H5 clade 2.3.4.4 viruses, a group of viruses that recently spread extensively in Asia and the US, shows in comparison a lower spatial extrapolation capacity than the HPAI H5N1 models, with a stronger association with intensively raised chicken densities and anthropogenic factors.

Human Monoclonal Antibody 81.39a Effectively Neutralizes Emerging Influenza A Viruses of Group 1 and 2 Hemagglutinins

The pandemic threat posed by emerging zoonotic influenza A viruses necessitates development of antiviral agents effective against various antigenic subtypes. Human monoclonal antibody (hMAb) targeting the hemagglutinin (HA) stalk offers a promising approach to control influenza virus infections. Here, we investigated the ability of the hMAb 81.39a to inhibit in vitro replication of human and zoonotic viruses, representing 16 HA subtypes. The majority of viruses were effectively neutralized by 81.39a at a 50% effective concentration (EC₅₀) of <0.01 to 4.9 μg/ml. Among group 2 HA viruses tested, a single A(H7N9) virus was not neutralized at 50 μg/ml; it contained HA₂-Asp19Gly, an amino acid position previously associated with resistance to neutralization by the group 2 HA-neutralizing MAb CR8020. Notably, among group 1 HA viruses, H11-H13 and H16 subtypes were not neutralized at 50 μg/ml; they shared the substitution HA₂-Asp19Asn/Ala. Conversely, H9 viruses harboring HA₂-Asp19Ala were fully susceptible to neutralization. Therefore, amino acid variance at HA₂-Asp19 has subtype-specific adverse effects on in vitro neutralization. Mice given a single injection (15 or 45 mg/kg of body weight) at 24 or 48 h after infection with recently emerged A(H5N2), A(H5N8), A(H6N1), or A(H7N9) viruses were protected from mortality and showed drastically reduced lung viral titers. Furthermore, 81.39a protected mice infected with A(H7N9) harboring HA₂-Asp19Gly, although the antiviral effect was lessened. A(H1N1)pdm09-infected ferrets receiving a single dose (25 mg/kg) had reduced viral titers and showed less lung tissue injury, despite 24- to 72-h-delayed treatment. Taken together, this study provides experimental evidence for the therapeutic potential of 81.39a against diverse influenza A viruses.

IMPORTANCE Zoonotic influenza viruses, such as A(H5N1) and A(H7N9) subtypes, have caused severe disease and deaths in humans, raising public health concerns. Development of novel anti-influenza therapeutics with a broad spectrum of activity against various subtypes is necessary to mitigate disease severity. Here, we demonstrate that the hemagglutinin (HA) stalk-targeting human monoclonal antibody 81.39a effectively neutralized the majority of influenza A viruses tested, representing 16 HA subtypes. Furthermore, delayed treatment with 81.39a significantly suppressed virus replication in the lungs, prevented dramatic body weight loss, and increased survival rates of mice infected with A(H5Nx), A(H6N1), or A(H7N9) viruses. When tested in ferrets, delayed 81.39a treatment reduced viral titers, particularly in the lower respiratory tract, and substantially alleviated disease symptoms associated with severe A(H1N1)pdm09 influenza. Collectively, our data demonstrated the effectiveness of 81.39a against both seasonal and emerging influenza A viruses.

Role for migratory wild birds in the global spread of avian influenza H5N8

Avian influenza viruses affect both poultry production and public health. A subtype H5N8 (clade 2.3.4.4) virus, following an outbreak in poultry in South Korea in January 2014, rapidly spread worldwide in 2014-2015. Our analysis of H5N8 viral sequences, epidemiological investigations, waterfowl migration, and poultry trade showed that long-distance migratory birds can play a major role in the global spread of avian influenza viruses. Further, we found that the hemagglutinin of clade 2.3.4.4 virus was remarkably promiscuous, creating reassortants with multiple neuraminidase subtypes. Improving our understanding of the circumpolar circulation of avian influenza viruses in migratory waterfowl will help to provide early warning of threats from avian influenza to poultry, and potentially human, health.

Novel Sequence-Based Mapping of Recently Emerging H5NX Influenza Viruses Reveals Pandemic Vaccine Candidates

Recently, an avian influenza virus, H5NX subclade 2.3.4.4, emerged and spread to North America. This subclade has frequently reassorted, leading to multiple novel viruses capable of human infection. Four cases of human infections, three leading to death, have already occurred. Existing vaccine strains do not protect against these new viruses, raising a need to identify new vaccine candidate strains. We have developed a novel sequence-based mapping (SBM) tool capable of visualizing complex protein sequence data sets using a single intuitive map. We applied SBM on the complete set of avian H5 viruses in order to better understand hemagglutinin protein variance amongst H5 viruses and identify any patterns associated with this variation. The analysis successfully identified the original reassortments that lead to the emergence of this new subclade of H5 viruses, as well as their known unusual ability to re-assort among neuraminidase subtypes. In addition, our analysis revealed distinct clusters of 2.3.4.4 variants that would not be covered by existing strains in the H5 vaccine stockpile. The results suggest that our method may be useful for pandemic candidate vaccine virus selection.

Investigating poultry trade patterns to guide avian influenza surveillance and control: a case study in Vietnam

Live bird markets are often the focus of surveillance activities monitoring avian influenza viruses (AIV) circulating in poultry. However, in order to ensure a high sensitivity of virus detection and effectiveness of management actions, poultry management practices features influencing AIV dynamics need to be accounted for in the design of surveillance programmes. In order to address this knowledge gap, a cross-sectional survey was conducted through interviews with 791 traders in 18 Vietnamese live bird markets. Markets greatly differed according to the sources from which poultry was obtained, and their connections to other markets through the movements of their traders. These features, which could be informed based on indicators that are easy to measure, suggest that markets could be used as sentinels for monitoring virus strains circulating in specific segments of the poultry production sector. AIV spread within markets was modelled. Due to the high turn-over of poultry, viral amplification was likely to be minimal in most of the largest markets. However, due to the large number of birds being introduced each day, and challenges related to cleaning and disinfection, environmental accumulation of viruses at markets may take place, posing a threat to the poultry production sector and to public health.

Widespread detection of highly pathogenic H5 influenza viruses in wild birds from the Pacific Flyway of the United States

A novel highly pathogenic avian influenza virus belonging to the H5 clade 2.3.4.4 variant viruses was detected in North America in late 2014. Motivated by the identification of these viruses in domestic poultry in Canada, an intensive study was initiated to conduct highly pathogenic avian influenza surveillance in wild birds in the Pacific Flyway of the United States. A total of 4,729 hunter-harvested wild birds were sampled and highly pathogenic avian influenza virus was detected in 1.3% (n = 63). Three H5 clade 2.3.4.4 subtypes were isolated from wild birds, H5N2, H5N8, and H5N1, representing the wholly Eurasian lineage H5N8 and two novel reassortant viruses. Testing of 150 additional wild birds during avian morbidity and mortality investigations in Washington yielded 10 (6.7%) additional highly pathogenic avian influenza isolates (H5N8 = 3 and H5N2 = 7). The geographically widespread detection of these viruses in apparently healthy wild waterfowl suggest that the H5 clade 2.3.4.4 variant viruses may behave similarly in this taxonomic group whereby many waterfowl species are susceptible to infection but do not demonstrate obvious clinical disease. Despite these findings in wild waterfowl, mortality has been documented for some wild bird species and losses in US domestic poultry during the first half of 2015 were unprecedented.

Global epidemiology of avian influenza A H5N1 virus infection in humans, 1997-2015: a systematic review of individual case data

Avian influenza viruses A(H5N1) have caused a large number of typically severe human infections since the first human case was reported in 1997. However, there is a lack of comprehensive epidemiological analysis of global human cases of H5N1 from 1997-2015. Moreover, few studies have examined in detail the changing epidemiology of human H5N1 cases in Egypt, especially given the most recent outbreaks since November 2014 which have the highest number of cases ever reported globally over a similar period. Data on individual cases were collated from different sources using a systematic approach to describe the global epidemiology of 907 human H5N1 cases between May 1997 and April 2015. The number of affected countries rose between 2003 and 2008, with expansion from East and Southeast Asia, then to West Asia and Africa. Most cases (67.2%) occurred from December to March, and the overall case fatality risk was 53.5% (483/903) which varied across geographical regions. Although the incidence in Egypt has increased dramatically since November 2014, compared to the cases beforehand there were no significant differences in the fatality risk , history of exposure to poultry, history of human case contact, and time from onset to hospitalization in the recent cases.

Cross-protection of newly emerging HPAI H5 viruses by neutralizing human monoclonal antibodies: A viable alternative to oseltamivir

Newly emerging highly pathogenic avian influenza (HPAI) H5N2, H5N3, H5N5, H5N6, H5N8 and H5N9 viruses have been spreading in poultry and wild birds. The H5N6 viruses have also caused 10 human infections with 4 fatal cases in China. Here, we assessed the cross-neutralization and cross-protection of human and mouse monoclonal antibodies against 2 viruses: a HPAI H5N8 virus, A/chicken/Netherlands/14015526/2014 (NE14) and a HPAI H5N6 virus, A/Sichuan/26221/2014 (SC14). The former was isolated from an infected chicken in Netherlands in 2014 and the latter was isolated from an infected human patient in Sichuan, China. We show that antibodies FLA5.10, FLD21.140, 100F4 and 65C6, but not AVFluIgG01, AVFluIgG03, S139/1 and the VRC01 control, potently cross-neutralize the H5N8 NE14 and H5N6 SC14 viruses. Furthermore, we show that a single injection of >1 mg/kg of antibody 100F4 at 4 hours before, or 20 mg/kg antibody 100F4 at 72 hours after, a lethal dose of H5N8 NE14 enables mice to withstand the infection. Finally, we show that a single injection of 0.5 or 1 mg/kg antibody 100F4 prophylactically or 10 mg/kg 100F4 therapeutically outperforms a 5-day course of 10 mg/kg/day oseltamivir treatment against lethal H5N8 NE14 or H5N6 SC14 infection in mice. Our results suggest that further preclinical evaluation of human monoclonal antibodies against newly emerging H5 viruses is warranted.

Highly pathogenic avian influenza viruses H5N2, H5N3, and H5N8 in Taiwan in 2015

A severe epidemic, affecting mainly goose populations, broke out in early January 2015. The causative agents were identified as novel H5 avian influenza viruses carrying N2, N3, and N8 subtypes of the neuraminidase gene. From January 8 to February 11, 766 waterfowl and poultry farms were invaded by the H5 viruses, and more than 2.2 million geese died or were culled. Phylogenetic analysis suggested that these avian influenza viruses derived from the H5 viruses of clade 2.3.4.4 which were emerging in 2014 in East Asia, West Europe, and North America.

Hemato-biochemical and pathological changes on avian influenza in naturally infected domestic ducks in Egypt

AIM

Few studies have been made in regard to avian influenza (AI) in ducks, thus the aim of this work was planned to investigate the hematological, biochemical, and pathological changes in domestic Egyptian ducks naturally infected with AI.

MATERIALS AND METHODS

30 duck from private backyards 3-month-old 15 were clinically healthy (Group 1) and the other fifteen (Group 2) were naturally diseased with AI (H5N1). The disease was diagnosed by polymerase chain reaction as H5N1.

RESULTS

Duck showed cyanosis, subcutaneous edema of head and neck with nervous signs (torticollis). Hematological studies revealed a microcytic hypochromic anemia. Biochemical studies revealed a significant decrease in total protein, albumin and globulin concentration with significant increase of activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, Υ-glutamyl transpeptidase, lactic acid dehydrogenase and creatine phsphokinase. Prominent increase in creatinine and uric acid in addition to hypocalcemia and hyperphosphatemia were significantly detected in the infected ducks. Histopathological finding confirm these investigations.

CONCLUSION

The highly pathogenic AIV (A/H5N1) became more severe infectious to ducks than before and causes nervous manifestations and blindness which were uncommon in ducks. Besides the significant increases of hepatic enzymes, brain, heart, and renal markers as a response to virus damage to these organs.

Wild waterfowl migration and domestic duck density shape the epidemiology of highly pathogenic H5N8 influenza in the Republic of Korea

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Phylogeographic analyses of H5N8, including 49 new sequences from South Korea.

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H5N8 movement was mostly among areas dense in wild and domestic ducks.

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New viral introductions to South Korea occurred at time of wild bird migration.

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H5N8 epidemiology is shaped by wild waterfowl migration and domestic duck density.

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H5N8 may have entered Europe at least twice, and Asia at least three times.

Highly pathogenic avian influenza (HPAI) viruses threaten human and animal health yet their emergence is poorly understood, partly because sampling of the HPAI Asian-origin H5N1 lineage immediately after its identification in 1996 was comparatively sparse. The discovery of a novel H5N8 virus in 2013 provides a new opportunity to investigate HPAI emergence in greater detail. Here we investigate the origin and transmission of H5N8 in the Republic of Korea, the second country to report the new strain. We reconstruct viral spread using phylogeographic methods and interpret the results in the context of ecological data on poultry density, overwintering wild bird numbers, and bird migration patterns. Our results indicate that wild waterfowl migration and domestic duck density were important to H5N8 epidemiology. Specifically, we infer that H5N8 entered the Republic of Korea via Jeonbuk province, then spread rapidly among western provinces where densities of overwintering waterfowl and domestic ducks are higher, yet rarely persisted in eastern regions. The common ancestor of H5N8 in the Republic of Korea was estimated to have arrived during the peak of inward migration of overwintering birds. Recent virus isolations likely represent re-introductions via bird migration from an as-yet unsampled reservoir. Based on the limited data from outside the Republic of Korea, our data suggest that H5N8 may have entered Europe at least twice, and Asia at least three times from this reservoir, most likely carried by wild migrating birds.