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PHNOM PENH, March 23 (Xinhua) -- A three-year-and-six-month boy from northeast Cambodia's Kratie province has been confirmed for H5N1 human avian influenza , raising the number of cases to three so far this year , said a Ministry of Health's statement on Sunday. The boy had been brought to the hospital in a critical condition with fever, cough, and dyspnea , it said, adding that he is receiving medical treatment with the utmost care from a team of doctors. "According to queries, the patient's family raised chickens and about five chickens had died , as some others were sick, and his family members cooked the dead poultry for food," the statement said. Health authorities are looking into the source of the infection and are examining any suspected cases or people who have been in contact with the patient in order to prevent an outbreak in the community, it added. Among the three human cases of H5N1 so far this year , two had died, and all patients reportedly had a h...

Abstract A sustained outbreak of H5N1 influenza virus among wild fowl and domestic livestock has caused more than 70 zoonotic infections in humans in the United States , including one death. The Centers for Disease Control and Prevention has recommended rapid H5 subtyping for all hospitalized cases with influenza A virus infection to enable prompt initiation of antiviral treatment , as well as infection prevention and implementation of public health measures to control spread. To address these needs, we developed a multiplex RT-qPCR assay to subtype H5 influenza virus in nasal, nasopharyngeal, and conjunctival specimens with a limit of detection of 230 copies/mL. No cross-reactivity was observed with other common respiratory viruses, including seasonal H3N2 and H1N1 influenza A viruses. We retrospectively subtyped 590 influenza A-positive clinical specimens processed by University of Washington labs between March 2024 and February 2025, including 512 specimens collected during the 2024...

{Excerpts} Recent updates Laboratory CDC completed serology testing on blood specimens from close contacts of a child with mild illness in San Francisco who was confirmed to be positive for avian influenza A(H5N1) virus, though, there were no known animal exposures associated with that case.  -- Serology testing was conducted to look for antibodies to influenza A(H5N1) virus in this child, which would indicate recent infection.  -- The child's blood was tested and found to have antibodies to avian influenza A(H5N1) virus.  -- None of the close contacts of the case in San Francisco who were tested had antibodies to avian influenza A(H5N1) virus, which supports the conclusion that none of these close contacts were infected , and that no person-to-person spread occurred among these close contacts.  -- These findings are reassuring. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States. CDC has sequenced the virus from...

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...

Abstract The current outbreak of highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype clade 2.3.4.4b in dairy cattle in the United States has affected nearly 900 dairy farms and resulted in at least 39 human infections, putting health authorities and the scientific community on high alert. Here we characterize the virus growth properties and host-pathogen interactions of an isolate obtained from a sick dairy cow in Texas in vitro and in vivo and compare it to an older HPAI isolate. Despite so far being associated with mild disease in human patients, the cattle H5N1 virus showed superior growth capability and rapid replication kinetics in a panel of human lung cell lines in vitro . In vivo, cattle H5N1 exhibited more intense pathogenicity in mice , with rapid lung pathology and high virus titers in the brain , accompanied by high mortality after challenge via different inoculation routes. Additionally, the cattle H5N1 demonstrated efficient antagonism of overexpressed RI...

Summary -- What is already known about this topic? -  Persons with occupational exposure to highly pathogenic avian influenza (HPAI) A(H5N1) virus–infected dairy cattle are at increased risk for infection. -- What is added by this report? -  During September 30–December 24, 2024, a total of 38 persons received a positive test result for HPAI A(H5N1) viruses in California ; 37 were dairy farm workers with occupational exposure to sick cows. One, a person aged <18 years with an undetermined exposure , was the first pediatric patient detected with influenza A(H5) infection in the United States. -- What are the implications for public health practice? -  Public health agencies should investigate influenza-like illness or conjunctivitis in workers with occupational exposure to animals infected with HPAI A(H5N1) virus. Thorough investigations of all human HPAI A(H5N1) virus infections are necessary to identify potential exposure sources, including monitoring the virus for co...

Highlights •  Scientific question :  Cross-species transmission of influenza A viruses from swine to humans occurs occasionally because their tracheal epitheliums possess both sialic acid α-2,6-Gal and α-2,3-Gal receptors . In 2011, the first human case of swine influenza virus infection in the mainland of China was detected in Jiangsu Province . Subsequently, the Eurasian avian-like H1N1 swine influenza virus (EAH1N1 SIV) had sporadically crossed the host barrier and infected humans, raising public concern for its pandemic potential. •  Evidence before this study :  A/Jiangsu/1/2011 (H1N1v) was first discovered in 2011 and belongs to the G1 genotype. The G4 and G5 genotypes that appeared successively in 2013 are recombinant H1N1 swine influenza viruses. The EAH1N1 SIVs from 2016 to the present are dominated by the G4 genotype, with hemagglutination (HA) and neuraminidase (NA) genes derived from the EAH1N1 SIVs, non-structural protein (NS) genes derived from the trip...

Highlights •  First isolation and molecular evidence of the subtype H3N2 in swine in Colombia . •  Swine H3N2 discovered is phylogenetically divergent from other viruses. •  Colombian H3N2 was originated from an independent human-to-swine spillover. •  Sequence-based analysis reveals this is a novel antigenic variant . •  Due to antigenic variation , Colombian H3N2 possess a relevant zoonotic risk. Abstract Influenza A virus (FLUAV) affects a wide range of hosts, including humans and animals, posing a threat to public health . In swine, H3N2 subtype is associated with human-to-swine spillovers of seasonal viruses . In Latin America , the molecular and antigenic characteristics of swine FLUAV H3N2, as well as its phylogenetic origin, are poorly understood. Therefore, the objective of this study was to characterize the first swine H3N2 detected in Colombia . The origin and lineage of the virus were estimated through phylogenetic and molecular clock analyses . Anti...

Abstract Since March 2024, highly pathogenic avian influenza A(H5N1) viruses have caused outbreaks in dairy cattle and poultry in the United States, and they continue to spill over into humans . However, data on human immune response to those viruses is limited. We report neutralizing antibody responses in 2 dairy farm worker H5N1 cases. Source: US Centers for Disease Control and Prevention,  https://wwwnc.cdc.gov/eid/article/31/4/25-0007_article ____

Abstract Background In late 2023, the first human case caused by an H10N5 avian influenza virus (AIV) was diagnosed in China . H10Ny AIVs have been identified in various poultry and wild birds in Eurasia, the Americas, and Oceania. Methods We analyzed the clinical data of the H10N5 AIV-infected patient, isolated the virus, and evaluated the virus receptor-binding properties together with the H10N8 and H10N3 AIVs identified in humans and poultry. The genomic data of the human-infecting H10N5 strain and avian H10Ny AIVs (n = 48, including 16 strains of H10N3 and 2 strains of H10N8) from live poultry markets in China , during 2019–2021, were sequenced. We inferred the genetic origin and spread pattern of the H10N5 AIV using the phylodynamic methods. In addition, given all available nucleotide sequences, the spatial-temporal dynamics, host distribution, and the maximum-likelihood phylogenies of global H10 AIVs were reconstructed. Findings The first H10N5 AIV-infected human case co-infected...

As of February 28, 2025 CDC assessed the risk from H5N1 viruses to the U.S. general population and to populations in the United States with contact with potentially infected animals, including through contaminated surfaces or fluids . Risk describes the potential public health implications and significance of an outbreak for populations assessed. See definitions below for more detail. {Risk posed by H5N1 viruses to the United States. Please see methods section for further information on definitions of terms.} ___ The purpose of this assessment is to evaluate the current public health risk of H5N1 viruses to the general U.S. population and to those in contact with potentially infected animals or contaminated surfaces or fluids, and to inform public health preparedness efforts. CDC assessed risk by considering both likelihood and impact of infection in each population (...). Both the likelihood and impact of infection are assessed at a population level. Likelihood of infection refers to ...

Abstract Highly pathogenic H5N1 avian influenza viruses (HPAIV) belonging to lineage 2.3.4.4b emerged in Chile in December 2022, leading to mass mortality events in wild birds, poultry, and marine mammals and one human case . We detected HPAIV in 7,33% (714/9745) of cases between December 2022–April 2023 and sequenced 177 H5N1 virus genomes from poultry, marine mammals, a human, and wild birds spanning >3800 km of Chilean coastline . Chilean viruses were closely related to Peru’s H5N1 outbreak, consistent with north-to-south spread down the Pacific coastline . One human virus and nine marine mammal viruses in Chile had the rare PB2 D701N mammalian-adaptation mutation and clustered phylogenetically despite being sampled 5 weeks and hundreds of kilometers apart . These viruses shared additional genetic signatures , including another mammalian PB2 adaptation (Q591K, n = 6), synonymous mutations, and minor variants. Several mutations were detected months later in sealions in the Atlanti...

Abstract Highly pathogenic avian influenza viruses (HPAIV) pose a serious public health concern . In March 2024, a first-time outbreak of HPAIV H5N1 in dairy cattle herds was reported in the United States (US). Since then, the virus has continued to spread in cattle herds and spilt over into humans . We recently showed that the first human isolate reported in the US in Texas (HPhTX) from a dairy worker in an affected cattle farm has enhanced replication kinetics and pathogenicity in mice compared to a closely related bovine isolate (HPbTX). However, the molecular determinants of differential pathogenicity have not yet been identified. Herein, we show that HPhTX has enhanced polymerase activity , compared with HPbTX, in human cells and that the polymerase basic 2 (PB2) protein is the main factor responsible for this difference. Through single and combined site-directed mutagenesis and swapping the three amino acids different between HPhTX and HPbTX, we found that PB2 mutation E627K is t...

ABSTRACT Coronaviruses (CoVs) pose a significant threat to public health , causing a wide spectrum of clinical manifestations and outcomes. Beyond precipitating global outbreaks, Human CoVs (HCoVs) are frequently found among patients with respiratory infections. To date, limited attention has been directed towards alphacoronaviruses due to their low prevalence and fatality rates . Nasal swab and serum samples were collected from a paediatric patient , and an epidemiological survey was conducted. Retrospective surveillance investigated the molecular prevalence of CoV in 880 rodents collected in the Republic of Korea (ROK) from 2018 to 2022. Next-generation sequencing (NGS) and phylogenetic analyses characterized the novel HCoV and closely related CoVs harboured by Apodemus spp . On 15 December 2022, a 103-day-old infant was admitted with fever, cough, sputum production, and rhinorrhea , diagnosed with human parainfluenza virus 1 (HPIV-1) and rhinovirus co-infection . Elevated AST/ALT le...

{Excerpts} (...) Epidemiology Updates As of February 24, CDC has confirmed three human cases of H5 bird flu in people who became ill in 2025:  -- a dairy worker with exposure to infected dairy cows (Nevada),  -- a poultry worker with exposure to infected commercial poultry ( Ohio ), and  -- the owner of an infected backyard poultry flock ( Wyoming ).  These are all considered higher-risk exposures . While the dairy worker was not hospitalized , both people with poultry exposures experienced severe illness and were hospitalized . Both hospitalized cases were confirmed positive from lower respiratory specimens , including a bronchoalveolar lavage and sputum . To date, there has been no evidence of onward spread from any of these people to anyone else . The dairy worker in Nevada had conjunctivitis (eye redness and irritation) and has recovered . Most infections associated with U.S. dairy cows to date have involved mild respiratory symptoms or conjunctivitis. This perso...

{Original text in Khmer} Ministry of Health Press Release A Fatal Case of #H5N1 #influenza in a 2-Year-7-Month-Old Child The Ministry of Health of the Kingdom of Cambodia wishes to inform the public that there are a  case of bird flu in a 2-year-old 7-month-old child has been confirmed positive for the influenza virus  H5N1 by the National Institute of Public Health on February 25, 2025. Location : Tangak Village, Romchek Commune, Preah Sdach District, Prey Veng Province. According to doctors , the child died on February 25, 2025 due to the parents  took the child to the hospital, when him developed a serious condition, including fever, cough, fatigue, and difficulty retreating. Severe breathing . According to the investigation, the patient's house has a family chicken farm and there are dead chickens.  About 15 of them were sick and the children were sleeping and playing in the basement near the chicken coop. The national and subnational emergency response teams of ...

Abstract In late 2021, Eurasian-lineage highly pathogenic avian influenza (HPAI) A(H5N1) viruses from HA clade 2.3.4.4b were first detected in the United States . These viruses have caused severe morbidity and mortality in poultry and have been detected in numerous wild and domestic animals , including cows and humans . Notably, infected cows transmitted the virus to cats , causing extreme pathogenicity and death. While human-to-human spread of the virus has not been recorded, efficient transmission of the bovine-origin virus has also led to extreme pathogenicity and death in ferret models . Recently, markers in PB2 (E627K) and HA (E186D, Q222H), indicating mammalian adaptation mutations , were detected in an H5N1-infected patient manifesting critical illness in Canada . These, combined with instances of interspecies spread of the virus , have raised global public health concerns. This could highlight the potential for the virus to successfully adapt to mammals, posing a serious risk o...

Abstract Highly Pathogenic Avian Influenza H5N1 (HPAI H5N1) was first detected in chickens in Scottland in 1959 and has since circulated globally, causing regular outbreaks among different animal species, as well as incidental infections in humans . In this scoping review, the epidemiology and impact of HPAI H5N1 among migratory birds, poultry, and cattle in the United States were analyzed, with a particular focus on outbreaks since January 2022. Following PRISMA guidelines, a total of 27 articles were identified for this review. Publicly available data and reports from the USDA and CDC were also evaluated and summarized. The identified articles primarily included epidemiological studies of detections in wild birds, mammals, and case reports on H5N1 and transmission dynamics among cattle , with a notable absence of poultry-focused reports . Wild birds, especially migratory species, have played an important role in virus dissemination. Studies among mammals , including seals, bears, and...

Abstract The emergence of highly pathogenic avian influenza A(H5N1) virus in dairy cattle herds across the United States in 2024 caused several human infections . Understanding the risk for spillover infections into humans is crucial for protecting public health. We investigated whether immunity from influenza A(H1N1)pdm09 (pH1N1) virus would provide protection from death and severe clinical disease among ferrets intranasally infected with H5N1 virus from dairy cows from the 2024 outbreak. We observed differential tissue tropism among pH1N1-immune ferrets. pH1N1-immune ferrets also had little H5N1 viral dissemination to organs outside the respiratory tract and much less H5N1 virus in nasal secretions and the respiratory tract than naive ferrets. In addition, ferrets with pH1N1 immunity produced antibodies that cross-reacted with H5N1 neuraminidase protein. Taken together, our results suggest that humans with immunity to human seasonal influenza viruses may experience milder disease fro...

Abstract In April 2024, Vietnam confirmed its first human case of influenza A(H9N2) in a 37-year-old man , marking a critical point in regional infectious disease monitoring and response. This case underscores the importance of robust surveillance systems and One Health collaboration in managing emerging zoonotic threats. Source: Emerging Infectious Diseases Journal,  https://wwwnc.cdc.gov/eid/article/31/2/24-1146_article ____