ETIDIOH - NEW

  ABSTRACT Current U.S. surveillance for highly pathogenic avian influenza A(H5N1) in humans prioritizes individuals with known animal exposures , potentially missing community-acquired infections . To address this gap, we implemented universal H5 subtyping of all influenza A-positive respiratory samples collected within our hospital system , regardless of patient exposure history. Between August 2024 and April 2025, we subtyped 4,488 influenza A-positive samples and identified two cases positive for H5 RNA in Alameda County, California, USA . The first case was a 14-month-old girl with mild respiratory symptoms and no H5N1 exposure risks ; sequencing of the sample revealed an H5 gene closely related to clade 2.3.4.4b, genotype B3.13 viruses circulating in U.S. dairies . The second case was a 79-year-old male, also with no known exposures , whose sample reproducibly tested positive with a high cycle threshold value but could not be confirmed by public health laboratories. Both pati...

  Abstract Selection of advantageous mutations drives the emergence of dominant variants during seasonal influenza epidemics . However, within-host detection of such variants remains rare , limiting our understanding of how selection operates at the scale of individual hosts. In this study, we used a controlled human infection model to examine the within-host evolutionary dynamics in thirteen participants intranasally infected with a seasonal H3N2 influenza A virus . Although this clinical trial is ongoing , our work represents a pre-planned, interim, exploratory analysis. Results in this system were contrasted with those observed in a ferret model of infection. The inoculum, used in both humans and ferrets, carried standing diversity that enabled evaluation of variant trajectories during infection. Although the dynamics were variable among participants, in humans , the minor variants in the PA and NP gene segments tended to increase in frequency as infection progressed. Variant dy...

  Abstract Highly pathogenic H5N1 avian influenza viruses of clade 2.3.4.4b cause sporadic human infections and currently raise concerns about a new influenza pandemic . Heterogeneities in disease severity have been observed in the past and are reported among infected farm workers in the United States . These may be attributed to differences in pre-existing H5N1 cross-reactive antibodies . In this study, we characterize H5N1 cross-reactive antibody landscapes in the current population (#NCT05794412 and #NCT01022905) and assess the effect of AS03-adjuvanted pandemic H1N1 and non-adjuvanted seasonal influenza vaccination on H5N1 cross-neutralizing and IgG antibody titers targeting a range of influenza virus-derived antigens. We detect H5N1 cross-neutralizing antibodies using a vesicular stomatitis virus-based pseudovirus system that correlate well with antibodies inhibiting the spread of authentic H5N1 viruses, anti-group 1 hemagglutinin stalk and anti-trimeric hemagglutinin antibodi...

  Abstract The highly pathogenic avian influenza viruses (HPAIV) of subtype H5N1 represent a major threat to animal and public health . The current panzootic with H5 clade 2.3.4.4b has caused numerous, widespread outbreaks in various domestic and wild avian species with high mortalities, massive losses and a high frequency of spillover events to unexpected novel mammalian hosts such as dairy cows . The global H5N1 situation raises serious concerns about zoonotic risks due to effective mammal-to-mammal transmission . Therefore, it is critical to increase surveillance intensity of a broadened species range, particularly at the human-animal interface . For this purpose, reliable and cost-effective serological tools that are easy to perform and suitable for high-throughput screenings are critically needed. The newly developed double antigen ELISA format employing a luminescence-based detection technology has demonstrated to comply with such prerequisites. The assay allowed the detectio...

  Abstract Avian influenza viruses (AIVs), including H5N1 and H7N9, from the Orthomyxoviridae family present substantial public health concerns . The predominant circulating clade 2.3.4.4b has demonstrated enhanced capacity for mammalian adaptation , raising concerns about potential reassortment with human seasonal influenza viruses . Unlike H7N9 ’s limited host range , H5N1 infects birds, various mammals, and humans . Recent concerns include widespread H5N1 infection of U.S. dairy cattle across 18 states , affecting over 1000 herds with 71 human infections (70 H5N1 and 1 H5N5). Key observations include cow-to-cow transmission, viral presence in milk, and transmission to humans , mainly through occupational exposure . Evidence of mammal-to-mammal transmission has been documented in European and Canadian foxes and South American marine mammals . Standard pasteurization effectively inactivates the virus in milk. The continuing mammalian adaptations , particularly mutations like PB2-E...

  Abstract Avian influenza is a global public health threat. Since 2021, the ongoing H5N1 panzootic has brought a major shift in H5Nx epidemiology , including unprecedented spread, wide host range and lack of seasonality . Infections in marine mammals, wildlife and livestock have heightened concern for human-to-human transmission and pandemic potential . Contact tracing and self-isolation are used as public health measures in the UK to manage contacts of confirmed human cases of avian influenza. In this study, we aimed to estimate potential outbreak sizes and evaluate the effectiveness of contact tracing and self-isolation in managing community outbreaks of H5N1 following spillover from birds to people . We characterised contact patterns from an underrepresented agricultural population at high risk of avian influenza exposure through contact with birds (Avian Contact Study). Informed by these realistic social contact data, we modelled outbreak sizes using a stochastic branching pro...

  Abstract Background Oropouche virus (OROV) is an emerging arbovirus primarily transmitted by biting midges and is increasingly recognized as a public health threat in Central and South America . With over 11,000 confirmed cases reported in 2024, a ten-fold increase from the previous year, its transmission dynamics and true burden remain poorly understood due to diagnostic challenges and fragmented surveillance systems. Objective This systematic review and meta-analysis (SRMA) synthesizes OROV prevalence data in humans and summarizes the available data for vectors and animal hosts sampled between 2000 and 2024 to provide updated estimates and identify key surveillance gaps. Methods We systematically searched Web of Science, PubMed, Embase, Medline, and LILACS for OROV seroprevalence and viral prevalence studies in human, insect, and animal populations, published up to September 12, 2024. The review protocol was registered with PROSPERO (CRD42024551000). Studies were extracted in d...

  Abstract Poultry workers in Washington, USA, were infected with highly pathogenic avian influenza A(H5N1) virus and recovered. The viruses were clade 2.3.4.4b genotype D1.1, closely related to viruses causing poultry outbreaks . Continued surveillance and testing for influenza A(H5) clade 2.3.4.4b viruses remain essential for risk assessment and pandemic preparedness of zoonotic influenza viruses. Source:  Link:  https://wwwnc.cdc.gov/eid/article/31/12/25-1118_article ____

{Excerpt}  Avian influenza A(H9N2) :  -- Guangdong Province :  1) An individual with onset in November 2025.  -- Guangxi Zhuang Autonomous Region :  2) An individual with onset in November 2025.  -- Hubei Province:  3) An individual with onset in November 2025.  (...) Source:  Link:  https://www.chp.gov.hk/files/pdf/2025_avian_influenza_report_vol21_wk51.pdf ____

  Influenza at the human-animal interface  Summary and risk assessment, from 6 November to 19 December 2025 {1} -- New human cases {1,2}:  - From 6 November to 19 December 2025, based on reporting date , the detection of influenza A( H5N1 ) in one human , A( H5N5 ) in one human , A( H9N2 ) in seven humans , and an influenza A( H1N1 ) variant virus in one human were reported officially.  - In addition , one human case of infection with an influenza A( H1N2 ) variant virus was detected.  -- Circulation of influenza viruses with zoonotic potential in animals :  - High pathogenicity avian influenza (HPAI) events in poultry and non-poultry animal species continue to be reported to the World Organisation for Animal Health (WOAH).{3}  - The Food and Agriculture Organization of the United Nations (FAO) also provides a global update on avian influenza viruses with pandemic potential.{4}  - Additionally, low pathogenicity avian influenza viruses as well a...

  Abstract Highly pathogenic avian influenza H5N1 poses an increasing public health risk, particularly following its spillover into dairy cows and associated human infections in the U.S. since March 2024. Here, we systematically identified critical PB2 mutations emerged during avian-to-cattle transmission and subsequent adaptation in cattle , notably PB2 M631L, which conferred pathogenicity in mice comparable to the well-characterized PB2 E627K mutation . Retrospective analysis reveals that PB2 631L also circulated in avian and human H5N1 strains during the 2013–2014 outbreaks in Cambodia and Vietnam . Additional adaptive mutations include established markers ( E627K, Q591R, D701N ), and novel variants ( I647V, G685R, K736R ). These mutations enhance polymerase activity by improving the utilization of both bovine and human ANP32A proteins , thereby increasing viral fitness and pathogenicity in mammals . The convergence of these adaptations highlights the elevated zoonotic risk of c...

  Abstract Highly Pathogenic Avian Influenza (HPAI) viruses, particularly IAV (H5N1), continue to pose a major global threat due to their widespread circulation and high mortality rates in birds. Management of HPAI is complicated by challenges in conserving migratory bird populations, sustaining poultry production, and uncertainties in disease dynamics. Structured decision-making frameworks , such as those based on the PrOACT model, are recommended to improve outbreak response and guide critical actions , especially when HPAI virus (HPAIV) detections occur in sensitive areas like wildlife refuges . Surveillance data from late 2024 to early 2025 show persistent HPAI activity , with 743 detections across 22 European countries and beyond, and notable outbreaks in poultry in nations like Hungary, Iceland, and the UK . The proximity of poultry farms to water sources increases environmental contamination risks. Meanwhile, HPAI A(IAV (H5N1)) and other H5Nx viruses have been detected in a ...

  Abstract The MERS-COV virus is a zoonotic coronavirus that emerged in 2012 in KSA and caused viral illness with a case fatality rate up to 35 %. Over a decade later, the virus is still evolving and circulating . The aim of this review is to discuss the current epidemiology of MERS-COV both in humans and animals, during and post the COVID-19 pandemic. We have found that MERS-COV is still evolving in camels with new lineages being detected in Saudi Arabia . Although the number of human cases has decreased , there is a gradual resurgence in the number of cases. Furthermore, many cases are being reported without exposure to camels and/or raw products, nor contact with known human cases . This necessitates global efforts in the surveillance of asymptomatic carriers in the community, role of unknown animal reservoirs in the virus spread if any, as well as extensive genomic surveillance of the virus. This is in order to unveil and assess the genetic changes that the virus is undergoing ...

  Abstract We describe the clinical symptoms and epidemiologic characteristics of a patient infected with avian influenza A(H10N3) virus in Guangxi Province , China , in December 2024. Whole-genome sequencing showed that the virus was highly homologous to a virus from Yunnan Province . H10 subtype viruses should be monitored for potential zoonotic or reassortant events. {From Emerging Infectious Diseases Journal, US CDC.} Sources:  Link:  https://pubmed.ncbi.nlm.nih.gov/41237415/ ____

  Abstract Highly pathogenic avian influenza H5N1 rarely infects mammals. In 2024-2025, however, genotypes B3.13 and D1.1 caused two independent spillovers into U.S. dairy cattle . By analysing 26,930 complete H5N1 genomes from global surveillance , we identified 73 major viral groups , most of which show continent-specific distribution in Europe, Asia, Africa , and North America . North American viruses exhibit higher genetic diversity in specific viral segments , including variants potentially associated with mammalian adaptation . Both dairy-cattle-associated B3.13 and D1.1 genotypes originate from the same geographic macro-area , suggesting a possible regional hotspot where avian-mammalian interfaces may facilitate viral adaptation. Our findings place the U.S. outbreaks in a global framework and indicate that North American H5N1 may be predisposed to cross-species transmission. Competing Interest Statement The authors have declared no competing interest. Funder Information Decl...

  Abstract The unprecedented 2.3.4.4b. A(H5N1) outbreak in dairy cattle, poultry, and spillover to humans in the United States (US) poses a major public health threat. Population immunity is a critical component of influenza pandemic risk assessment . We assessed the pre-existing cross-reactive immunity to 2.3.4.4b A(H5N1) viruses and analyzed 1794 sera from 723 people (0.5–88 yrs) in multiple US geographic regions during 2021–2024. Pre-existing neutralizing and hemagglutinin (HA)-head- binding antibodies to A(H5N1) were low , but there were substantial cross-reactive binding antibodies to N1 neuraminidase (NA) of 2.3.4.4b A(H5N1). Antibodies to group 1 HA stalk were also prevalent and increased with age . A(H1N1)pdm09 infection and influenza vaccination did not induce neutralizing antibodies to A(H5N1) viruses but induced significant rise of functional NA inhibition (NAI) antibodies to N1 of 2.3.4.4b A(H5N1), and group 1 HA stalk antibodies . Moreover, pre-pandemic stockpiled 2.3....

{Excerpt} Country 2024 (cases - deaths) - 2025 (cases - deaths) - Total (cases - deaths) 1) Australia - 1 - 0 - 0 - 0 - 1 - 0   2) Azerbaijan - ... - ... - 0 - 0 - 8 - 5  3) Bangladesh - ... - ... -  3 - 0 - 11 - 1  4) Cambodia - 10 - 2 - 17 - 8 - 89 - 51  5) Canada - 1 - 0 - 0 - 0 - 2 - 1  6) Chile - ... - ... - 0 - 0 - 1 - 0  7) China - 1 - 0 - 1 - 0 - 57 - 32  8) Djibouti - ... - ... - 0 - 0 - 1 - 0  9) Ecuador - ... - ... - 0 - 0 - 1 - 0  10) Egypt - ... - ... - 0 - 0 - 359 - 120  11) India - ... - ... - 2 - 2 - 3 - 3  12) Indonesia - ... - ... - 0 - 0 - 200 - 168  13) Iraq - ... - ... - 0 - 0 - 3 - 2  14) Lao People's Democratic Republic - ... - ... - 0 - 0 - 3 - 2  15) Mexico - ... - ... - 1 - 1 - 1 - 1  16) Myanmar - ... - ... - 0 - 0 - 1 - 0  17) Nepal - ... - ... - 0 - 0 - 1 - 1  18) Nigeria - ... - ... - 0 - 0 - 1 - 1  19) Pakistan - ... - ... - 0 - 0 - 3 - 1  20) Spain - ... - ...

  Abstract Avian influenza viruses (AIVs) pose a significant zoonotic threat, with the emerging H3N8 subtype raising increasing concern due to sporadic human infections . Current strategies for risk assessment of novel AIVs primarily rely on genetic surveillance and isolated case reports, which provide limited insight into their cross-species transmission potential . However, these approaches may overlook critical phenotypic determinants , such as pathogenicity, transmissibility, and environmental persistence , that directly influence zoonotic risk . This study investigates the evolutionary relationships , receptor-binding properties, replication dynamics, pathogenicity in mice, transmission efficiency in guinea pigs, and environmental persistence of three H3N8 strains isolated from a live poultry market . All three H3N8 strains bound exclusively to α-2,3 sialic acid receptor and achieved 100% transmissibility among guinea pigs through direct contact . Notably, the environment-orig...