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Understanding the transmission routes of high-pathogenicity avian influenza (HPAI) is crucial for developing effective control measures to prevent its spread. In this context, windborne transmission, the idea that the virus could travel through the air over considerable distances, is a contentious concept, and documented cases have been rare. Here, though, we provide genetic evidence supporting the feasibility of windborne transmission. During the 2023−24 HPAI season, molecular surveillance identified identical H5N1 strains among a cluster of unrelated commercial farms about 8 km apart in the Czech Republic. The episode started with the abrupt mortality of fattening ducks on one farm. This was followed by disease outbreaks at two nearby high-biosecurity chicken farms. Using genetic, epizootiological, meteorological and geographical data, we reconstructed a mosaic of events strongly suggesting wind was the most probable mechanism of infection transmission between poultry in at least two independent cases. By aligning the genetic and meteorological data with critical outbreak events, we determined the most likely time window during which the transmission occurred and inferred the sequence of infected houses at the recipient sites. Our results suggest that the contaminated plume emitted from the infected fattening duck farm was the critical medium of HPAI transmission, rather than the dust generated during depopulation. Furthermore, our results also strongly implicate the role of confined mechanically-ventilated buildings with high population densities in facilitating windborne transmission and propagating virus concentrations below the minimum infectious dose at the recipient sites. These findings underscore the importance of considering windborne spread in future outbreak mitigation strategies.

Recently, continuing outbreaks of avian influenza in China have not only caused great loss to the agricultural sector but also brought fear and distrust to consumers, seriously undermining consumer confidence in chicken products. We investigated consumers’ purchase intentions during avian influenza outbreaks by examining a regionally representative sample of 330 consumers in Guangzhou. With respect to 7 kinds of attributes, the ordered logit analysis indicated that possible health threat and uncertainty of the origin of poultry products may cause concern among consumers and cause them to avoid purchasing chicken products. Media reports have a great influence on consumers’ intentions to purchase chicken products during avian influenza outbreaks. Overall, this study suggests establishing an effective mechanism of public knowledge (of chicken products’ safety and quality) enhancement, in order to curb misleading media reports during avian influenza outbreaks.

Following confirmation of the first case of the ongoing U.S. HPAI H5N1 epizootic in commercial poultry on February 8, 2022, the virus has continued to devastate the U.S. poultry sector and the pathogen has since managed to cross over to livestock and a few human cases have also been reported. Efficient outbreak management benefits greatly from timely detection and proper identification of the pathways of virus introduction and spread. In this study, we used changes in mortality rates as a proxy for HPAI incidence in a layer, broiler and turkey flock together with diagnostic test results to infer within-flock HPAI transmission dynamics. Mathematical modeling techniques, specifically the Approximate Bayesian Computation algorithm in conjunction with a stochastic within-flock HPAI transmission model were used in the analysis. The time window of HPAI virus introduction into the flock (TOI) and the adequate contact rate (ACR) were estimated. Then, using the estimated TOI together with the day when the first HPAI positive sample was collected from the flock, we calculated the most likely time to first positive sample (MTFPS) which reflects the time to HPAI detection. The estimated joint (i.e., all species combined) median of the MTFPS for different flocks was six days, the joint median most likely ACR was 6.8 newly infected birds per infectious bird per day, the joint median R 0 was 13 and the joint median number of test days per flock was two. These results were also grouped by species and by epidemic phase and discussed accordingly. We conclude that this findings from this and other related studies are beneficial for the different stakeholders in outbreak management. We recommend that combining TOI analysis with complementary approaches such as phylogenetic analyses is critically important for improved understanding of disease transmission pathways. The estimated parameters can also be used to parametrize mathematical models that can guide the design of surveillance protocols, risk analyses of HPAI spread, and emergency preparedness for HPAI outbreaks.

Spillover of Highly Pathogenic Avian Influenza (HPAI) to backyard poultry via migratory birds threatens the poultry industry and public health. To improve the understanding of spillover events, we developed a stochastic compartmental mathematical model of HPAI transmission dynamics at the waterfowl-backyard poultry interface in a high-risk area for HPAI introduction into poultry. The model described the infection spread among resident and migratory waterfowl and backyard poultry farms and was validated with historical outbreak data in backyard poultry farms and swan mortalities. We used the model to assess the impact of the timing and duration of migratory birds’ stopover period on the probability of HPAI infection in backyard poultry farms. Additionally, we predicted mortality in a sentinel bird species and assessed the impact of HPAI virulence and immunity in a resident reservoir species on the HPAI transmission dynamics. The stopover duration of the reservoir species predicts the HPAI infection probability in backyard poultry farms from waterfowl communities, but the stopover timing has no effect. HPAI virus virulence and immunity against the virus impact the transmission risk to backyard poultry. Understanding factors influencing reservoir species’ migration stopover duration in a location will aid HPAI outbreak forecasting and control in backyard poultry farms.

High pathogenicity avian influenza (HPAI) continues to be a major threat to poultry production in Bangladesh, where poultry is a primary source of affordable protein and outbreaks also pose zoonotic risks to humans. We conducted a cross-sectional study in 331 commercial broiler, layer, and Sonali poultry farms to evaluate biosecurity and farm management practices across different poultry production systems in relation to government-recommended biosecurity guidelines, and to identify risk factors associated with avian influenza (AI) outbreaks, as well as to assist in mitigating AI outbreak risks and improving disease prevention in poultry farms. We found that 93.4% of farms were in residential areas and 68.8% of the farms were near waterbodies. A significant number of farms had access to domestic and wild animals, with limited implementation of disinfection and hygiene practices. Overall, most farms did not fully comply with government suggested standard biosecurity and good farm management guidelines. In total, 51 (15.4%) farms reported AI outbreaks with the highest proportion in layer farms (29.1%), followed by broiler (10.6%) and Sonali (7.8%). AI outbreaks were significantly associated with outbreak history on nearby farms, farmers or workers visiting other farms, and farm management by workers or multiple individuals rather than owners. Veterinarian visits were also found to be associated with outbreaks on farms, which may reflect reporting bias rather than causality. Our findings underscore that substantial gaps in biosecurity compliance remain widespread across all farm types. We recommend strengthening biosecurity protocols, addressing environmental risks, and providing comprehensive training programs for farmers to control AI spread, prevent future outbreaks, and ultimately safeguard both poultry and public health.

Avian metapneumovirus (aMPV), classified within the Pneumoviridae family, wreaks havoc on poultry health. It typically causes upper respiratory tract and reproductive tract infections, mainly in turkeys, chickens, and ducks. Four subtypes of AMPV (A, B, C, D) and two unclassified subtypes have been identified, of which subtypes A and B are widely distributed across the world. In January 2024, an outbreak of severe respiratory disease occurred on turkey and chicken farms across different states in the US. Metagenomics sequencing of selected tissue and swab samples confirmed the presence of aMPV subtype B. Subsequently, all samples were screened using an aMPV subtype A and B multiplex real-time RT-PCR kit. Of the 221 farms, 124 (56%) were found to be positive for aMPV-B. All samples were negative for subtype A. Six whole genomes were assembled, five from turkeys and one from chickens; all six assembled genomes showed 99.29 to 99.98% nucleotide identity, indicating a clonal expansion event for aMPV-B within the country. In addition, all six sequences showed 97.74 to 98.58% nucleotide identity with previously reported subtype B sequences, e.g., VCO3/60616, Hungary/657/4, and BR/1890/E1/19. In comparison to these two reference strains, the study sequences showed unique 49–62 amino acid changes across the genome, with maximum changes in glycoprotein (G). One unique AA change from T (Threonine) to I (Isoleucine) at position 153 in G protein was reported only in the chicken aMPV sequence, which differentiated it from turkey sequences. The twelve unique AA changes along with change in polarity of the G protein may indicate that these unique changes played a role in the adaptation of this virus in the US poultry. This is the first documented report of aMPV subtype B in US poultry, highlighting the need for further investigations into its genotypic characterization, pathogenesis, and evolutionary dynamics.

Introduction For a decade, avian influenza (AI) viruses were major concern for Egypt since they are endemic in poultry and have caused 359 human infections, accounting for 40% of cases globally. Interventions implemented before 2015 proved to have minor impact on the spread of infection. Since 2015, a Supported Intervention Package (SIP) was implemented to reduce the risk of human exposure by reducing infections in poultry. The intervention package included enhanced surveillance and laboratory capacity, early outbreak detection, and raised community awareness. This study aims to evaluate SIP’s effectiveness by comparing number and rates of AI in humans and poultry before and after intervention package implementation. Methods AI surveillance data for poultry and humans from 2006 to 2021 was obtained and linked. Human AI data include patients’ demographics, clinical picture, risk factors, lab results and outcome, while poultry data include number prevent of positive specimens for AI by time and place. Confirmation performed by testing oropharyngeal swabs collected from suspected patients and poultry using RT-PCR in the affiliated laboratory. Positive rates were calculated, descriptive data analysis was performed and rate of infection was plotted against demographics and risk factors. Results compared before and after implementation of using Chi 2 and t-test with p  < 0.05 significance. Results Among all confirmed cases, 346(96.4%) reported before and 13(3.6%) after SIP implementation with no cases reported after 2017. A significant reduction in positivity rate of both human and poultry cases (2.0 vs. 0.2% and 2.4 vs. 1.2%, p  < 0.001) found after 2015. Percent of housewives decreased from 30.9 to 7.7%, p  < 0.05 and positive specimens’ rates from backyards decreased from 61.1 to 47.9%, p  < 0.001. Median days to laboratory confirmation reduced from 3.6 to 2.8 days. The genetic analysis indicated a major genetic drift occurred before 2015, possibly due to inadequate control measures. Conclusions The Study indicated reduced infections in humans and poultry suggesting effectiveness of SIP, which also raised community awareness as shown by reducing infections among housewives and enhancing surveillance as shown by case earlier detection. Continued coordinated efforts between human and poultry sectors are needed to contribute to the elimination of the disease in Egypt.

Since its first isolation from migratory birds in Egypt in 2016, highly pathogenic avian influenza (HPAI) H5N8 has caused several outbreaks among domestic poultry in various areas of the country affecting poultry health and production systems. However, the genetic and biological properties of the H5N8 HPAI viruses have not been fully elucidated yet. In this study, we aimed to monitor the evolution of circulating H5N8 viruses and identify the pathogenicity and mammalian adaptation in vitro and in vivo . Three H5N8 HPAI viruses were used in this study and were isolated in 2021–2022 from poultry and wild birds during our routine surveillance. RNA extracts were subjected to full genome sequencing. Genetic, phylogenetic, and antigenic analyses were performed to assess viral characteristics and similarities to previously isolated viruses. Phylogenetic analysis showed that the hemagglutinin genes of the three isolates belonged to clade 2.3.4.4b and grouped with the 2019 viruses from G3 with high similarity to Russian and European lineages. Multiple basic amino acids were observed at cleavage sites in the hemagglutinin proteins of the H5N8 isolates, indicating high pathogenicity. In addition, several mutations associated with increased virulence and polymerase activity in mammals were observed. Growth kinetics assays showed that the H5N8 isolate is capable of replicating efficiently in mammalian cells lines. In vivo studies were conducted in SPF chickens (White Leghorn), mice, and hamsters to compare the virological characteristics of the 2022 H5N8 isolates with previous H5N8 viruses isolated in 2016 from the first introduction. The H5N8 viruses caused lethal infection in all tested chickens and transmitted by direct contact. However, we showed that the 2016 H5N8 virus causes a higher mortality in chickens compared to 2022 H5N8 virus. Moreover, the 2022 virus can replicate efficiently in hamsters and mice without preadaptation causing systemic infection. These findings underscore the need for continued surveillance of H5 viruses to identify circulating strains, determine the commercial vaccine’s effectiveness, and identify zoonotic potential.

A/goose/Guangdong/1/96-like (GsGd) highly pathogenic avian influenza (HPAI) H5 viruses cause severe outbreaks in poultry when introduced. Since emergence in 1996, control measures in most countries have suppressed local GsGd transmission following introductions, making persistent transmission in domestic birds rare. However, geographical expansion of clade 2.3.4.4 sublineages has raised concern about establishment of endemic circulation, while mechanistic drivers leading to endemicity remain unknown. We reconstructed the evolutionary history of GsGd sublineage, clade 2.3.4.4c, in Taiwan using a time-heterogeneous rate phylogeographic model. During Taiwan’s initial epidemic wave (January 2015 - August 2016), we inferred that localised outbreaks had multiple origins from rapid spread between counties/cities nationwide. Subsequently, outbreaks predominantly originated from a single county, Yunlin, where persistent transmission harbours the trunk viruses of the sublineage. Endemic hotspots determined by phylogeographic reconstruction largely predicted the locations of re-emerging outbreaks in Yunlin. The transition to endemicity involved a shift to chicken-dominant circulation, following the initial bidirectional spread between chicken and domestic waterfowl. Our results suggest that following their emergence in Taiwan, source-sink dynamics from a single county have maintained GsGd endemicity up until 2023, pointing to where control efforts should be targeted to eliminate the disease. Highly pathogenic H5 avian influenza viruses of the A/Goose/Guangdong/96-like lineage spread globally and have become endemic in some locations. Here, the authors perform phylogenetic analyses to describe the dynamics of this lineage as it transitioned from causing sporadic outbreaks to becoming endemic in Taiwan.

In late November 2014 higher than normal death losses in a meat turkey and chicken broiler breeder farm in the Fraser Valley of British Columbia initiated a diagnostic investigation that led to the discovery of a novel reassortant highly pathogenic avian influenza (HPAI) H5N2 virus. This virus, composed of 5 gene segments (PB2, PA, HA, M and NS) related to Eurasian HPAI H5N8 and the remaining gene segments (PB1, NP and NA) related to North American lineage waterfowl viruses, represents the first HPAI outbreak in North American poultry due to a virus with Eurasian lineage genes. Since its first appearance in Korea in January 2014, HPAI H5N8 spread to Western Europe in November 2014. These European outbreaks happened to temporally coincide with migratory waterfowl movements. The fact that the British Columbia outbreaks also occurred at a time associated with increased migratory waterfowl activity along with reports by the USA of a wholly Eurasian H5N8 virus detected in wild birds in Washington State, strongly suggest that migratory waterfowl were responsible for bringing Eurasian H5N8 to North America where it subsequently reassorted with indigenous viruses.