Virus Clade Research Articles

Influenza A(H5N1) Virus Clade 2.3.2.1a in Traveler Returning to Australia from India, 2024.

We report highly pathogenic avian influenza A(H5N1) virus clade 2.3.2.1a in a child traveler returning to Australia from India. The virus was a previously unreported reassortant consisting of clade 2.3.2.1a, 2.3.4.4b, and wild bird low pathogenicity avian influenza gene segments. These findings highlight surveillance gaps in South Asia.

2024 Mpox outbreak: A rapidly evolving public health emergency of international concern

The declaration of a second Public Health Emergency of International Concern (PHEIC) for mpox in August 2024 underscores the urgent need for a comprehensive understanding of the evolving epidemiology [1] clinical manifestations, and zoonotic potential of this emerging threat [2]. This work delves into the intricate interplay between human and animal mpox infections, with a specific focus on the unique characteristics of various viral clades and their implications for individual and public health.There is a critical need to elucidate the factors driving multiple spillover events and the subsequent emergence of new clades better adapted to human-to-human transmission. We hypothesize that anthropogenic changes, including deforestation, urbanization, and climate change are facilitating increased human-to-animal contact, leading to more frequent zoonotic transmissions and viral adaptations. Our conceptual framework integrates One Health principles, evolutionary virology, and epidemiological modeling to investigate the demographic, clinical, and treatment differences among mpox clades in both humans and animals. We employ a mixed-methods approach, combining genomic analysis, clinical data review, and ecological surveys to construct a comprehensive picture of mpox's changing dynamics. The research questions explore the differences in epidemiological and clinical profiles among mpox clades and the factors that likely contribute to successful cross-species transmission and human adaptation.This manuscript introduces an updated Identify, Isolate, Inform (3I) Tool meticulously redesigned to significantly improve the early detection, containment, and reporting of mpox cases across diverse settings. By integrating clinical, virological, and ecological data, this work aims to lay the groundwork for enhanced risk assessment, targeted interventions, and global preparedness strategies in the face of this evolving zoonotic threat.

First case of mpox with monkeypox virus clade Ib outside Africa in a returning traveller, Sweden, August 2024: public health measures.

An unprecedented upsurge in mpox, caused by clade I of the monkeypox virus (MPXV) was noted in Central Africa in 2024. The first mpox case with MPXV clade Ib outside Africa was reported in Sweden in mid-August. The case experienced a mild disease course after travelling to an affected country. No additional cases of this clade have been detected in Sweden. Strengthened public health measures and surveillance including whole genome sequencing are crucial to prevent establishment of novel MPXV clades.

Epidemiological data of an influenza A/H5N1 outbreak in elephant seals in Argentina indicates mammal-to-mammal transmission

H5N1 high pathogenicity avian influenza virus has killed thousands of marine mammals in South America since 2022. Here we report epidemiological data and full genome characterization of clade 2.3.4.4b H5N1 HPAI viruses associated with a massive outbreak in southern elephant seals (Mirounga leonina) at Península Valdés, Argentina, in October 2023. We also report on H5N1 viruses in concurrently dead terns. Our genomic analysis shows that viruses from pinnipeds and terns in Argentina form a distinct clade with marine mammal viruses from Peru, Chile, Brazil and Uruguay. Additionally, these marine mammal clade viruses share an identical set of mammalian adaptation mutations which were also present in tern viruses. Our combined ecological and phylogenetic data support mammal-to-mammal transmission and occasional mammal-to-bird spillover and suggest multinational transmission of H5N1 viruses in mammals. We reflect that H5N1 viruses becoming more evolutionary flexible and adapting to mammals in new ways could have global consequences for wildlife, humans, and/or livestock.

Reassortants of the Highly Pathogenic Influenza Virus A/H5N1 Causing Mass Swan Mortality in Kazakhstan from 2023 to 2024.

In the winter of 2023/2024, the mass death of swans was observed on Lake Karakol on the eastern coast of the Caspian Sea. From 21 December 2023 to 25 January 2024, 1132 swan corpses (Cygnus olor, Cygnus cygnus) were collected and disposed of on the coast by veterinary services and ecologists. Biological samples were collected from 18 birds for analysis at different dates of the epizootic. It was found that the influenza outbreak was associated with a high concentration of migrating birds at Lake Karakol as a result of a sharp cold snap in the northern regions. At different dates of the epizootic, three avian influenza A/H5N1 viruses of clade 2.3.4.4.b were isolated from dead birds and identified as highly pathogenic viruses (HPAIs) based on the amino acid sequence of the hemagglutinin multi-base proteolytic cleavage site (PLREKRRRKR/G). A phylogenetic analysis showed that the viruses isolated from the swans had reassortations in the PB2, PB1, and NP genes between highly pathogenic (HP) and low-pathogenic (LP) avian influenza viruses. Avian influenza viruses A/Cygnus cygnus/Karakol lake/01/2024(H5N1) and A/Mute swan/Karakol lake/02/2024(H5N1) isolated on 10 January 2024 received PB2, PB1, and NP from LPAIV, while A/Mute swan/Mangystau/9809/2023(H5N1) isolated on 26 December 2023 received PB1 and NP from LPAIV, indicating that the H5N1 viruses in this study are new reassortants. All viruses showed amino acid substitutions in the PB2, PB1, NP, and NS1 segments, which are critical for enhanced virulence or adaptation in mammals. An analysis of the genomes of the isolated viruses showed that bird deaths during different periods of the epizootic were caused by different reassortant viruses. Kazakhstan is located at the crossroads of several migratory routes of migratory birds, and the possible participation of wild birds in the introduction of various pathogens into the regions of Kazakhstan requires further study.

Dominant HPAIV H5N1 genotypes of Germany 2021/2022 are linked to high virulence in Pekin ducklings

Highly pathogenic avian influenza viruses (HPAIV) of H5 clade 2.3.4.4b pose an ongoing threat worldwide. It remains unclear whether this panzootic situation would favor low virulent phenotypes expected by the ‘avirulence hypothesis’ of viral evolution. Assessing virulence in Pekin ducklings in an intramuscular infection model revealed that the two genotypes that dominated the epidemiological situation in Germany during the period 2021 and 2022 (EU-RL:CH and EU-RL:AB) were of high virulence. In contrast, rare genotypes were of intermediate virulence. The genetic constellation of these reassortants pointed to an important role of the viral polymerase complex (RdRP), particularly the PB1 genome segment, in shaping virulence in ducklings. Occulo-nasal infection of ducklings confirmed the phenotypes for two representative viruses and indicated a more efficient replication for the high virulence strain. These observations would be in line with the ‘virulence-transmission trade-off’ model for describing HPAIV epidemiology in wild birds in Germany.

Measures of Population Immunity Can Predict the Dominant Clade of Influenza A (H3N2) in the 2017-2018 Season and Reveal Age-Associated Differences in Susceptibility and Antibody-Binding Specificity.

For antigenically variable pathogens such as influenza, strain fitness is partly determined by the relative availability of hosts susceptible to infection with that strain compared with others. Antibodies to the hemagglutinin (HA) and neuraminidase (NA) confer substantial protection against influenza infection. We asked if a cross-sectional antibody-derived estimate of population susceptibility to different clades of influenza A (H3N2) could predict the success of clades in the following season. We collected sera from 483 healthy individuals aged 1 to 90 years in the summer of 2017 and analyzed neutralizing responses to the HA and NA of representative strains using focus reduction neutralization tests (FNRT) and enzyme-linked lectin assays (ELLA). We estimated relative population-average and age-specific susceptibilities to circulating viral clades and compared those estimates to changes in clade frequencies in the following 2017-2018 season. The clade to which neutralizing antibody titers were lowest, indicating greater population susceptibility, dominated the next season. Titer correlations between viral strains varied by age, suggesting age-associated differences in epitope targeting driven by shared past exposures. Yet substantial unexplained variation remains within age groups. This study indicates how representative measures of population immunity might improve evolutionary forecasts and inform selective pressures on influenza.

Development of a multiplex droplet digital PCR method for detection and differentiation of mpox virus clades

BackgroundThe current outbreak of mpox has been declared a public health emergency of international concern by the World Health Organization. However, distinguishing symptoms of mpox virus (MPXV) infection from other orthopoxviruses is atypical, necessitating laboratory confirmatory tests to aid in clinical diagnosis. Therefore, rapid and accurate detection and differentiation of various clades of MPXV are imperative. ObjectiveA multiplex droplet digital PCR (ddPCR) method was developed to detect and differentiate various clades of MPXV with subsequent evaluation of its sensitivity and accessibility through the analysis of 17 clinical samples. MethodsPrimers and probes for multiple ddPCR were designed by comparing multiple complete genomes of orthopoxviruses. Primer and probe concentrations, reaction conditions were tentatively optimized on the Biorad QX200 platform. Seventeen clinical samples of MPXV were detected and verified by Sanger sequencing. ResultsThe established ddPCR method could detect and differentiate MPXV, and the results were consistent with those of Sanger sequencing. ConclusionMultiplex ddPCR could be used to detect and distinguish different clades of MPXV rapidly and accurately.

A comprehensive epidemiological approach documenting an outbreak of H5N1 highly pathogenic avian influenza virus clade 2.3.4.4b among gulls, terns, and harbor seals in the Northeastern Pacific.

Highly pathogenic avian influenza viruses (HPAIV) H5N1 clade 2.3.4.4b continue to have unprecedented global impacts on wild birds and mammals, with especially significant mortality observed in colonial surface-nesting seabirds and in some marine mammal species. In July of 2023 H5N1 HPAIV 2.3.4.4b was detected in Caspian terns nesting on Rat Island, Washington USA. An estimated 1,800-1,900 adult terns populated the breeding colony, based on aerial photographs taken at the start of the outbreak. On a near-weekly basis throughout July and August, we counted and removed carcasses, euthanized moribund birds, and collected swab and tissue samples for diagnostic testing and next-generation sequencing. We directly counted 1,101 dead Caspian tern adults and 520 dead chicks, indicating a minimum 56% loss of the adult colony population and potential impacts to reproductive success. Combining the observed mortality on Rat Island with HPAI-related Caspian tern deaths recorded elsewhere in Washington and Oregon, we estimate that 10-14% of the Pacific Flyway population was lost in the summer of 2023. Comparatively few adult Glaucous-winged gulls (hybrids) nesting on Rat Island died (~3% of the local population), although gull chick mortality was high. Sixteen harbor seals in the immediate or nearby area stranded during the outbreak, and H5N1 HPAIV was detected in brain and/or lung tissue of five seals. These cases are the first known detections of HPAIV in a marine mammal on the Pacific coast of North America. Phylogenetic analyses support the occurrence of at least three independent avian-mammalian virus spillover events (tern or gull to harbor seal). Whole genome sequencing indicated that H5N1 HPAIV may have been introduced to Washington from Caspian terns in Oregon. Ongoing monitoring and surveillance for H5N1 HPAIV in the marine environment is necessary to understand the epidemiology of this virus, assess conservation impacts to susceptible species, and provide support for data-driven management and response actions.

Molecular characterisation of human rabies in Tanzania and Kenya: a case series report and phylogenetic investigation

BackgroundRabies remains a major public health problem in low- and middle-income countries. However, human rabies deaths are rarely laboratory-confirmed or sequenced, especially in Africa. Five human rabies deaths from Tanzania and Kenya were investigated and the causative rabies viruses sequenced, with the aim of identifying implications for rabies control at individual, healthcare and societal levels.Case presentationThe epidemiological context and care of these cases was contrasting. Four had a clear history of being bitten by dogs, while one had an unclear biting history. Two individuals sought medical attention within a day of being bitten, whereas three sought care only after developing rabies symptoms. Despite seeking medical care, none of the cases received complete post-exposure prophylaxis: one patient received only tetanus vaccination, one did not complete the post-exposure vaccination regimen, one followed an off-label vaccination schedule, and two did not receive any post-exposure vaccinations before the onset of symptoms. These cases highlight serious gaps in health-seeking behaviour, and in health systems providing appropriate care following risky exposures, including in the accessibility and effectiveness of post-exposure prophylaxis as it is administered in the region.ConclusionsThe viral genomic and epidemiological data confirms dog-mediated rabies as the cause of each of these deaths. The phylogenetic investigation highlights the transboundary circulation of rabies within domestic dog populations, revealing distinct rabies virus clades with evidence of regional spread. These findings underscore the importance of coordinated cross-border control efforts between the two countries. Urgent action is needed to improve awareness around the need for emergency post-exposure vaccines that should be accessible in local communities and administered appropriately, as well as investment in coordinated dog vaccination to control dog-mediated rabies, the underlying cause of these deaths.Graphical

Monkeypox Clade Ib virus introduction into Burundi: first findings, July to mid-August 2024.

We describe cases with monkeypox virus (MPXV) Clade Ib in Burundi from their first detection in July until 20 August 2024. Testing 442 people with vesicular lesions confirmed 170 cases (98 male; 72 female), 82 (48%) being < 15 years old. Differential diagnosis of the first 30 individuals testing MPXV negative revealed chickenpox in 20. Cases occurred in 26 of 49 Burundi health districts, but mostly in Bujumbura Nord (88/170; 67%). Case-derived MPXV genetic sequences from Burundi and South-Kivu (Democratic Republic of the Congo), clustered together in phylogenetic analysis.

Diagnostic and surveillance testing capability for mpox in the EU/EEA, September 2024.

In response to the increasing number of mpox cases caused by monkeypox virus (MPXV) clade I in the African continent and the first reported travel-related clade Ib case of mpox in EU/EEA, the European Centre for Disease Prevention and Control surveyed national capability for detection and characterisation of MPXV in the EU/EEA. The results showed high level of capability for case confirmation by PCR, alongside molecular typing methods for identification of MPXV clades and/or clade I subclades within the EU/EEA.

Genetic features of avian influenza (A/H5N8) clade 2.3.4.4b isolated from quail in Egypt

Several genotypes of the highly pathogenic avian influenza (HPAI) virus H5N8 subtype within clade 2.3.4.4b continue to circulate in different species of domestic birds across Egypt. It is believed that quail contribute to virus replication and adaptation to other gallinaceous poultry species and humans. This study provides genetic characterization of the full genome of HPAI H5N8 isolated from quail in Egypt. The virus was isolated from a commercial quail farm associated with respiratory signs. To characterize the genetic features of the detected virus, gene sequencing via Sanger technology and phylogenetic analysis were performed. The results revealed high nucleotide identity with the HPAI H5N8 virus from Egypt, which has multiple basic amino acid motifs PLREKRRKR/GLF at the hemagglutinin (HA) cleavage site. Phylogenetic analysis of the eight gene segments revealed that the quail isolate is grouped with HPAI H5N8 viruses of clade 2.3.4.4b and closely related to the most recent circulating H5N8 viruses in Egypt. Whole-genome characterization revealed amino acid preferences for avian receptors with few mutations, indicating their affinity for human-like receptors and increased virulence in mammals, such as S123P, S133A, T156A and A263T in the HA gene. In addition, the sequencing results revealed a lack of markers associated with influenza antiviral resistance in the neuraminidase and matrix-2 coding proteins. The results of the present study support the spread of HPAIV H5N8 to species other than chickens in Egypt. Therefore, continuous surveillance of AIV in different bird species in Egypt followed by full genomic characterization is needed for better virus control and prevention.

Genetic sequencing analysis of monkeypox virus clade I in Republic of the Congo: a cross-sectional, descriptive study

Monkeypox virus clade I is endemic in several central African countries and characterised by an increase in disease severity and mortality. Since October, 2023, a large-scale mpox outbreak has emerged in DR Congo, and in March, 2024, the first individuals with mpox were reported outside the endemic areas in Republic of the Congo. We aimed to provide insight into the epidemic by sequencing samples obtained from individuals with mpox in Republic of the Congo. In this cross-sectional, descriptive study, samples were collected from individuals with suspected mpox between Jan 15 and April 8, 2024, in Brazzaville, Pointe-Noire, Likouala, Cuvette-Centrale, and Plateaux (Republic of the Congo). Blood samples, skin or oropharyngeal swabs, or skin crusts were obtained for molecular diagnosis via real-time PCR. Monkeypox virus sequences were obtained and analysed using newly established nanopore sequencing methodology and bioinformatic pipeline. The sequences obtained were aligned and used to construct a maximum likelihood phylogenetic tree using IG-TREE. 61 samples were collected from individuals with suspected mpox, 31 of which were positive for monkeypox virus and were included in our analysis (four positive samples were excluded due to unavailability of epidemiological data or insufficient biological material). Individuals who tested positive for monkeypox virus were from Cuvette-Centrale (19 [61%] of 31), Likouala (eight [26%]), and Pointe-Noire (four [13%]). 20 (65%) were male and 11 (35%) were female. Phylogenetic analysis of sequences showed two major clusters within clade Ia. One cluster was made up of four sequences from this study clustering with two monkeypox virus sequences from the current DR Congo outbreak, three older sequences from Central African Republic sequenced between 2017 and 2018, and seven sequences from DR Congo sequenced in 2006-07 and 2022. The second cluster was made up of 16 sequences from this study clustering with sequences from the current DR Congo outbreak. In addition, sequences from Republic of the Congo show multiple phylogenetic positioning suggesting the occurrence of multiple co-circulating strains in the human population. Our findings suggest that multiple monkeypox virus strains are co-circulating in the human population, highlighting the need for implementation of expanded mpox surveillance, especially in countries bordering DR Congo and Republic of the Congo, in combination with control measures focused on containing the current outbreaks in these countries to prevent escalation into a larger-scale epidemic. Intramural Research Program of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

Measures of population immunity can predict the dominant clade of influenza A (H3N2) in the 2017-2018 season and reveal age-associated differences in susceptibility and antibody-binding specificity.

For antigenically variable pathogens such as influenza, strain fitness is partly determined by the relative availability of hosts susceptible to infection with that strain compared to others. Antibodies to the hemagglutinin (HA) and neuraminidase (NA) confer substantial protection against influenza infection. We asked if a cross-sectional antibody-derived estimate of population susceptibility to different clades of influenza A (H3N2) could predict the success of clades in the following season. We collected sera from 483 healthy individuals aged 1 to 90 years in the summer of 2017 and analyzed neutralizing responses to the HA and NA of representative strains using Focus Reduction Neutralization Tests (FNRT) and Enzyme-Linked Lectin Assays (ELLA). We estimated relative population-average and age-specific susceptibilities to circulating viral clades and compared those estimates to changes in clade frequencies in the following 2017-18 season. The clade to which neutralizing antibody titers were lowest, indicating greater population susceptibility, dominated the next season. Titer correlations between viral strains varied by age, suggesting age-associated differences in epitope targeting driven by shared past exposures. Yet substantial unexplained variation remains within age groups. This study indicates how representative measures of population immunity might improve evolutionary forecasts and inform selective pressures on influenza.

Continuing evolution of H5N1 highly pathogenic avian influenza viruses of clade 2.3.2.1a G2 genotype in domestic poultry of Bangladesh during 2018–2021

ABSTRACT We characterized 15 H5N1 HPAI viruses from different small- and medium-scale poultry flocks across Bangladesh during 2018–2021 based on their complete genome sequences. The antigenic relatedness of H5N1 HPAI viruses from different timepoints was analysed. During 2020–2021, 42.11% of the flocks tested positive for at least one of the respiratory infections, with 15.79% showing influenza A virus, of which 8.77% tested positive for HPAIV H5N1. Co-infections with two to four pathogens were detected in 15.8% of flocks. Phylogeny and gene constellation analyses based on complete genome sequences of 15 HPAI viruses revealed the continuing circulation of H5 clade 2.3.2.1a genotype G2 viruses. In the HA protein of the study isolates, functionally meaningful mutations caused the loss of an N-linked glycosylation site (T156A), a modified antigenic site A (S141P), and a mutation in the receptor binding pocket (E193R/K). Consequently, antigenic analysis revealed a significant loss of cross-reactivity between viruses from different host species and periods. Most viruses displayed oseltamivir resistance markers at positions V96, I97, S227, and N275 (N1 numbering) of the NA protein. In addition, for the PB2, M1, and NS1 proteins, significant mutations were noticed that have been associated with polymerase activity and increased virulence for mammals in all study isolates. These results highlight the need for intensified genomic surveillance of HPAI circulating in poultry in Bangladesh and for establishing appropriate control measures to decrease the circulation of these viruses in poultry in the country.

An Analysis of Combined Molecular Weight and Hydrophobicity Similarity between the Amino Acid Sequences of Spike Protein Receptor Binding Domains of Betacoronaviruses and Functionally Similar Sequences from Other Virus Families

Recently, we proposed a new method, based on protein profiles derived from physicochemical dynamic time warping (PCDTW), to functionally/structurally classify coronavirus spike protein receptor binding domains (RBD). Our method, as used herein, uses waveforms derived from two physicochemical properties of amino acids (molecular weight and hydrophobicity (MWHP)) and is designed to reach into the twilight zone of homology, and therefore, has the potential to reveal structural/functional relationships and potentially homologous relationships over greater evolutionary time spans than standard primary sequence alignment-based techniques. One potential application of our method is inferring deep evolutionary relationships such as those between the RBD of the spike protein of betacoronaviruses and functionally similar proteins found in other families of viruses, a task that is extremely difficult, if not impossible, using standard multiple alignment-based techniques. Here, we applied PCDTW to compare members of four divergent families of viruses to betacoronaviruses in terms of MWHP physicochemical similarity of their RBDs. We hypothesized that some members of the families Arteriviridae, Astroviridae, Reoviridae (both from the genera rotavirus and orthoreovirus considered separately), and Toroviridae would show greater physicochemical similarity to betacoronaviruses in protein regions similar to the RBD of the betacoronavirus spike protein than they do to other members of their respective taxonomic groups. This was confirmed to varying degrees in each of our analyses. Three arteriviruses (the glycoprotein-2 sequences) clustered more closely with ACE2-binding betacoronaviruses than to other arteriviruses, and a clade of 33 toroviruses was found embedded within a clade of non-ACE2-binding betacoronaviruses, indicating potentially shared structure/function of RBDs between betacoronaviruses and members of other virus clades.

Hepatitis Delta Virus Clade 8 Is the Predominant Clade Circulating in Botswana amongst People Living with HIV.

Hepatitis delta virus (HDV) co-infections more often result in severe hepatitis compared to hepatitis B virus (HBV) infections alone. Despite a high HDV prevalence (7.1%), information regarding circulating HDV clades is very limited in Botswana. We extracted total nucleic acid from confirmed HDV-positive samples and quantified their viral load. We then sequenced the large hepatitis delta antigen (L-HDAg) using Oxford Nanopore Technology (ONT). Genotyping was performed using the HDV Database, and HDV mutation profiling was performed on AliView. All participants with HBV genotypic information belonged to sub-genotype A1, and 80% (4/5) of them had a higher HDV viral load and a lower HBV viral load. We sequenced 75% (9/12) of the HDV-positive samples, which belonged to HDV clade 8. A total of 54 mutations were discovered, with the most prevalent being Q148R (16%), D149P (16%) and G151D (16%). Known mutations such as S117A, K131R, R139K and G151D were detected, while the other mutations were novel. Our results reveal that HDV clade 8 is the predominant clade in Botswana. The significance of all mutations remains unclear. Future studies with a larger sample size to detect other HDV clades that might be circulating in Botswana and functionally characterize the detected mutations are warranted.

Avian Influenza: Lessons from Past Outbreaks and an Inventory of Data Sources, Mathematical and AI Models, and Early Warning Systems for Forecasting and Hotspot Detection to Tackle Ongoing Outbreaks.

The ongoing avian influenza (H5N1) outbreak, one of the most widespread and persistent in recent history, has significantly impacted public health and the poultry and dairy cattle industries. This review covers lessons from past outbreaks, risk factors for transmission, molecular epidemiology, clinical features, surveillance strategies, and socioeconomic impacts. Since 1997, H5N1 has infected over 900 individuals globally, with a fatality rate exceeding 50%. Key factors influencing infection rates include demographic, socioeconomic, environmental, and ecological variables. The virus's potential for sustained human-to-human transmission remains a concern. The current outbreak, marked by new viral clades, has complicated containment efforts. This review discusses how to integrate technological advances, such as mathematical modeling and artificial intelligence (AI), to improve forecasting, hotspot detection, and early warning systems. We provide inventories of data sources, covering both conventional and unconventional data streams, as well as those of mathematical and AI models, which can be vital for comprehensive surveillance and outbreak responses. In conclusion, integrating AI, mathematical models, and technological innovations into a One-Health approach is essential for improving surveillance, forecasting, and response strategies to mitigate the impacts of the ongoing avian influenza outbreak. Strengthening international collaboration and biosecurity measures will be pivotal in controlling future outbreaks and protecting both human and animal populations from this evolving global threat.

Highly Pathogenic Avian Influenza A Virus in Wild Migratory Birds, Qinghai Lake, China, 2022.

In July 2022, an outbreak of highly pathogenic avian influenza A(H5N1) virus clade 2.3.4.4b occurred among migratory birds at Qinghai Lake in China. The virus circulated in June, and reassortants emerged after its introduction into the area. Surveillance in 2023 showed that the virus did not establish a stable presence in wild waterfowl.