ETIDIOH - NEW

  Abstract Since 2021, subclade 2.3.4.4b A(H5N1) high pathogenicity avian influenza (HPAI) viruses have undergone changes in ecology and epidemiology, causing a panzootic of unprecedented scale in wild and domestic birds with spill-over infections and perceptible transmission in a range of mammalian species , raising concern over zoonotic potential . HPAI viruses readily exchange gene segments with low pathogenicity avian influenza viruses via reassortment , a mechanism that facilitates pronounced phenotypic change . Observations suggest changes in the seasonality and host range of panzootic viruses, however, data on the role of reassortment in determining such features are limited. Using phylodynamic approaches, we describe the emergence of the panzootic lineage and using a novel global genotype classification system we describe the subsequent emergence and global structuring of genotypes generated by reassortment. Focusing on evolutionary dynamics in Europe , we show reassortment...

Abstract Avian influenza viruses undergo frequent genetic reassortment, which can coincide with phenotypic changes in transmission, pathogenicity, and host species niche . Since 2020, clade 2.3.4.4b H5 high pathogenicity avian influenza viruses (HPAIVs) have driven a global panzootic , causing mass mortality in wild birds, poultry , and, for the first time, repeated spillover infections in a variety of mammalian species . This resurgence of H5 HPAIV has coincided with a dramatic increase in the number of circulating reassortant strains ; however, the scale, impact and drivers of these reassortants remain unknown. Here, we combined statistical and phylodynamic modelling to reconstruct the global evolutionary dynamics of H5Nx viruses across four epizootic seasons (2020-2024). We identified 209 genetically distinct reassortants , stratified into three transmission categories based on their phylogenetic and epidemiological profiles. Accounting for sampling depth and HPAIV incidence, we est...

Abstract Highly pathogenic avian influenza (HPAI) has become a critical threat to wildlife, shifting from a seasonal epizootic to a persistent, year-round panzootic with global consequences . Here, we summarize the origin, evolutionary mechanisms, and expanding host range of the current H5N1 virus (clade 2.3.4.4b) and assess its impact on wildlife . Over the past five years, HPAI has caused the deaths of millions of wild birds , causing dramatic population declines in several seabird species . However, comprehensive quantitative mortality data remain scarce, as existing records are often anecdotal, focus on localized mass die-offs, and thus represent only a fraction of the true magnitude of mortality. This gap in data limits the ability to predict outbreak dynamics and mitigate long-term consequences. Using the Northwestern European Sandwich Tern (Thalasseus sandvicensis) population as a case study, we demonstrate the value of integrating mortality data with ecological, serological and...

Abstract Avian influenza (AI) is a highly contagious viral disease affecting poultry and wild water birds , posing significant global challenges due to its high mortality rates and economic impacts. Highly pathogenic avian influenza (HPAI) outbreaks , particularly those caused by H5N1 and its variants , have surged since their first occurrence in 1959. The HPAI H5N1 clade 2.3.4.4b viruses have notably expanded its geographical reach, affecting numerous countries, diverse avian species, and now wild and domestic mammals . Using an ecological niche modelling approach, this study aims to elucidate the environmental factors associated with the increased HPAI H5 cases since 2020, investigate potential shifts in ecological niches , and predict new areas suitable for local viral circulation. Focusing on H5N1 and H5Nx strains, we have developed ecological niche models for HPAI case in both wild and domestic birds while considering two distinct periods: 2015-2020 and 2020-2022. Key environmenta...

Abstract Since their first detection in 1996, highly pathogenic avian influenza viruses with H5 haemagglutinin of the A/Goose/Guangdong/1/1996 (Gs/Gd) lineage have caused outbreaks in domestic and wild animals associated with mass morbidity and mortality , and economic losses as well as sporadic human infections . These viruses have spread to hosts across the European, Asian, African, and North and South American continents, and most recently Antarctica , representing a major threat to wildlife, domestic animals and humans . Owing to continuous circulation in poultry, Gs/Gd lineage viruses have diversified into numerous distinct genetic and antigenic (sub)clades , and genetic diversity has further increased by extensive reassortment with low pathogenic avian influenza viruses of wild birds. In this Review, we discuss the historical emergence of Gs/Gd lineage viruses and their evolution and geographical spread . An overview of the major determinants of host range and cross-species trans...

ABSTRACT The H5N1 avian panzootic has resulted in cross-species transmission to birds and mammals, causing outbreaks in wildlife, poultry, and US dairy cattle with a range of host-dependent pathogenic outcomes . Although no human-to-human transmission has been observed, the rising number of zoonotic human cases creates opportunities for adaptive mutation or reassortment . This Gem explores the history, evolution, virology, and epidemiology of clade 2.3.4.4b H5N1 relative to its pandemic potential. Pandemic risk reduction measures are urgently required. Source: Journal of Virology,  https://journals.asm.org/doi/full/10.1128/jvi.02209-24?af=R ____

Abstract H5N1 influenza has been circulating in birds from Eurasia and Africa for more than 146 years , but human infection has been sporadic. H5N1 (clade 2.3.4.4b) has recently infected hundreds of species of wild and domestic birds and mammals in North America . Furthermore, as of February 26, 2025, H5N1 has infected 70 humans in the United States , and one infection proved lethal . Furthermore, in attempts to control H5N1 in the United States, 10s of millions of egg-laying chickens have died or been culled . These efforts have led to very high egg prices in the United States. We have developed an analytical bioinformatics and genomics workflow to understand better how H5N1 is circulating in North America and adapting to new host species . Our workflow consists of: 1) Phylogenetic analyses of large viral sequence datasets to identify subclades of viral lineages causing the current outbreaks in humans and farm animals and closely related viral background lineages. 2) Next, we transfer...

According to CCTV News, on December 18 local time, California Governor Gavin Newsom declared a state of emergency in California to deal with the increasingly serious avian influenza epidemic . Although there have been no cases of human-to-human transmission in California , 61 people have been infected with avian influenza in the United States, 34 of which are from California . Newsom emphasized that although the risk is low, the government will continue to take necessary measures to prevent the spread of the virus and open funds to support the emergency response of relevant agencies. According to Xinhua News Agency, the U.S. Centers for Disease Control and Prevention issued a statement on the 18th saying that the United States reported the first severe case of human infection with the H5N1 avian influenza virus . The patient was hospitalized and his infection may be related to contact with sick and dead poultry raised in private backyard farms. The CDC said in a statement that the pati...

In an update on the mutating virus - known as H5N1 – Dr. Madhur Dhingra from the Food and Agriculture Organization, FAO, said that it had “spilled over into wildlife”.  More than 500 bird species have been infected along with at least 70 mammalian species , including the endangered California condor and polar bears .  In regions that are heavily reliant on poultry as a primary source of protein, the FAO medic insisted that avian influenza “poses a serious threat to food and nutrition security”. Economic damage Dr Dhingra warned that hundreds of millions of people’s livelihoods have been affected by the virus – an economic burden on farmers that could prevent them from investing in adequate biosafety measures. Following the emergence of H5N1 influenza virus in dairy cattle , the WHO has joined calls for strengthened surveillance and biosecurity on farms, to keep animals and people safe. The UN health agency said that in 2024, 76 people have been infected with the H5 avian influ...