Emergence and #Evolution of Triple #Reassortant Highly Pathogenic Avian #Influenza #H5N1 Virus, #Argentina, 2025

 

Abstract

The H5N1 subtype of highly pathogenic avian influenza (HPAI) poses a major zoonotic threat due to its high fatality rate and capacity for cross species transmission. In early 2025, Argentina detected a novel triple reassortant A(H5N1) virus in Chaco Province, combining Eurasian, North American, and South American lineage segments. Genomic analyses of subsequent outbreaks in Buenos Aires and Entre Ríos confirmed persistence of this reassortant and additional HA substitutions (T204K, P251S) potentially linked to increased mammalian receptor affinity. Although PB2 sequences lacked canonical mammalian-adaptive markers (E627K, Q591K, D701N), all contained I292M, a mutation associated with human adaptation. Phylogenetic analyses revealed distinct genotypes and increasing divergence. These findings indicate ongoing viral evolution and adaptation within Argentina, emphasizing the urgent need for sustained genomic surveillance, timely data sharing, and integrated One Health strategies to mitigate zoonotic and socioeconomic risks associated with H5N1 spread in South America.

Source: 

Link: https://www.mdpi.com/1999-4915/18/5/525

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#Argentina - #Influenza A #H5 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

{A Coscoroba Swan. By Charles J. Sharp - Own work, from Sharp Photography, sharpphotography.co.uk, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=179069673}

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{A Black-Necked Swan. By Charles J. Sharp - Own work, from Sharp Photography, sharpphotography.co.uk, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=178158764}

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{A Fulvous Whistling Duck. By JeffreyGammon - Own work, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=158156460}

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{A Brown-Hooded Gull. By Charles J. Sharp - Own work, from Sharp Photography, sharpphotography.co.uk, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=179073441}

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Contact with wild migratory birds present in the area is presumed to be the likely source of infection. Virological analysis has identified the presence of the H5 subtype of high pathogenicity avian influenza (HPAI). The determination of the neuraminidase subtype is pending in order to complete the characterisation of the pathogenic agent. Further information is provided in the epidemiological comments of the outbreak.

Source: 

Link: https://wahis.woah.org/#/in-review/7291

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#Argentina - High pathogenicity avian #influenza #H5 viruses (Inf. with) (#poultry) - Immediate notification

 

At a heavy breeding poultry farm located in the province of Buenos Aires, an increase in mortality and the presence of clinical signs consistent with high pathogenicity avian influenza (HPAI) were observed. Given the clinical suspicion, official intervention was carried out, including a health inspection and the collection of diagnostic samples for processing. Laboratory analyses confirmed a positive result for high pathogenicity avian influenza subtype H5 (HPAI H5).

The event occured on a farm raising heavy breeding stock. On 21/02/2026, the National Service of Agri-Food Health and Quality (SENASA) received a notification concerning mortality and clinical signs consistent with high pathogenicity avian influenza (HPAI) which began on 19/02/2026, as reported by the reporting person. On 22/02/2026, the suspicion was officially addressed with the restriction of the establishment and taking of samples for official diagnosis. On 23/02/2026, the samples tested positive for HPAI H5. All the birds on the establishment will be culled. We will update the population data in subsequent follow-up reports.

Source: 

Link: https://wahis.woah.org/#/in-review/7290

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Novel Highly Pathogenic Avian #Influenza #H5N1 Virus, #Argentina, 2025

 

Abstract

Genomic sequencing of reemerging highly pathogenic avian influenza A(H5N1) virus detected in Argentina in February 2025 revealed novel triple-reassortant viruses containing gene segments from Eurasian H5N1 and low pathogenicity viruses from South and North American lineages. Our findings highlight continued evolution and diversification of clade 2.3.4.4b H5N1 in the Americas.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/31/12/25-0783_article

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Spatial #Variation of #SARS-CoV-2 #Exposure in Urban #Rodents from the Metropolitan Area of Buenos Aires, #Argentina: Implications for Public Health in Latin American Cities

 

Abstract

Background: 

The COVID-19 pandemic, driven by the SARS-CoV-2 virus, has become an unprecedented global public health challenge. Comprehensive investigation of the virus transmission dynamics requires exploration of all potential routes, including the role of animal reservoirs. This study aimed to assess the presence of SARS-CoV-2 RNA and antibodies in urban rodents captured within two landscape units (low-income neighborhoods and green spaces) in the metropolitan area of Buenos Aires (MABA), Argentina.

Methods: 

Between July 2020 and September 2022, 125 synanthropic rodents (68 Rattus norvegicus, 22 R. rattus, and 35 Mus musculus) from seven low-income neighborhoods and seven green spaces in the MABA were captured and examined for SARS-CoV-2 exposure and infection by indirect immunofluorescence serology and RT-qPCR, targeting the N, E, and ORF1ab genes.

Results: 

Two M. musculus and six R. norvegicus from five different low-income neighborhoods tested positive for SARS-CoV-2 antibodies. No rodent with positive serology was detected in green spaces. All rodents tested negative for SARS-CoV-2 RNA when analyzed by RT-qPCR.

Conclusion: 

The results of this study provide valuable insights into the ecological dynamics of SARS-CoV-2 in synanthropic rodents in two landscape units within a Latin American city, with seropositive rodents detected in low-income neighborhoods, suggesting a possible increased exposure risk in these settings. This information is critical for developing management strategies for potentially zoonotic viruses and underscores the importance of continued surveillance of SARS-CoV-2 in rodents as part of an integrated One Health approach.

Source: Vector-Borne and Zoonotic Diseases, https://www.liebertpub.com/doi/abs/10.1177/15303667251389403

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#Argentina - #Influenza A #H5 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

The Official Veterinary Service was informed of dead birds and signs consistent with highly pathogenic avian influenza (HPAI) in a backyard in the province of Buenos Aires. On the same day, the suspicion was dealt with and samples were taken for testing. The samples were tested by the official laboratory and were positive for HPAI H5.

On 6th October 2025, the Official Veterinary Service was informed of two birds dead in a backyard at Azcuénaga, province of Buenos Aires. The suspicion was dealt with and samples were taken for testing. The samples were sent to the official SENASA laboratory on 7th October 2025 and on the same day, positive results were obtained for HPAI H5 clade 2.3.4.4; all the birds were killed and disposed of, and the premises was cleaned and disinfected. The affected backyard is less than 2 kilometers from the Giles River, so contact with wild birds is suspected.

Source: WOAH, https://wahis.woah.org/#/in-review/6855

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#Argentina - High pathogenicity avian #influenza #H5 viruses (#poultry) (Inf. with) - Immediate notification

The event occurred in a laying hen farm in the province of Buenos Aires. The birds involved showed mortality and clinical signs consistent with high pathogenicity avian influenza. The suspicion is officially addressed and samples were taken. The samples tested positive for HPAI H5.

The event occurred in a laying hen farm. On 17/08/25 National Service of Agri-Food Health and Quality (SENASA) received a notification concerning mortality and clinical signs consistent with high pathogenicity avian influenza (HPAI) (drooping and diarrhea). The suspicion is officially addressed, with restriction of the establishment and taking of samples for diagnosis. On 19/08/2025, samples tested positive for HPAI H5. The stamping out of all the birds in the establishment will be carried out. We will update the population data in the following follow-up reports.

Source: WOAH, https://wahis.woah.org/#/in-review/6737

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#Argentina - #Influenza A #H5 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

The Official Veterinary Services received a notification concerning bird mortality and signs consistent with high pathogenicity avian influenza (HPAI) in a backyard in the Buenos Aires province. On the same day, the suspicion was addressed and samples were taken for analysis. The samples were analysed by the Official Laboratory and came back positive for HPAI H5 clade 2.3.4.4. The affected premises are adjacent to bodies of water, so contact with wild birds is presumed

On 14/07/2025, the Official Veterinary Services received a notification concerning bird mortality and signs consistent with high pathogenicity avian influenza (HPAI) in a backyard in the town of Lezama, in the Buenos Aires province. On the same day, the suspicion was addressed and samples were taken for analysis. On 15/07/2025 the samples were analysed by the Official Laboratory and came back positive for HPAI H5 clade 2.3.4.4. The species involved are chickens, peacocks, pheasants and guinea fowl. The affected premises are adjacent to bodies of water, so contact with wild birds is presumed. Stamping out and disposal of all the birds will be carried out, as well as cleaning and disinfection of the premises. We will update the population information in subsequent follow-up reports.

Source: WOAH, https://wahis.woah.org/#/in-review/6630

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Virological characterization of a new isolated strain of #Andes virus involved in recent person-to-person #transmission #outbreak reported in #Argentina

Abstract

On November 2, 2018, a person-to-person transmission outbreak of Andes virus (Orthohantavirus andesense) began in the small town of Epuyén, Argentina. The strain demonstrated a high capacity for sustained transmission among the human population requiring the implementation of quarantine measures, rigorous contact tracing, isolation of close contacts, and active clinical monitoring to prevent further spread. In this study, we report the isolation of this strain, which we name the ARG-Epuyén strain, directly from a clinical sample after just three passages in cell culture. Complete sequencing revealed only a single amino acid change post-isolation, suggesting that this strain can be considered a non-adapted wild-type Andes virus, marking a critical step toward the development of medical countermeasures against this emerging pathogen. The pathogenicity and transmissibility potential of ARG-Epuyén were evaluated in hamsters, the only animal model for Hantavirus Pulmonary Syndrome. Additionally, this strain was compared with Andes/ARG, an ANDV strain previously isolated from the same geographical area in the Argentinian Patagonia, from a rodent specimen. Our findings revealed high infectiousness and efficient hamster-to-hamster transmission through direct contact experiments, although ARG-Epuyén appeared to be less pathogenic than Andes/ARG.

Source: PLoS Neglected Tropical Diseases, https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013205

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Novel Highly Pathogenic Avian #Influenza A #H5N1 Triple #Reassortant in #Argentina, 2025

Abstract

Genomic sequencing of re-emerging highly pathogenic avian influenza A(H5N1) virus detected in Argentina in February 2025 revealed novel triple-reassortant viruses containing gene segments from Eurasian H5N1 and low pathogenic viruses from South and North American lineages. These findings underscore continued evolution and diversification of clade 2.3.4.4b H5N1 in the Americas.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.05.23.655175v1

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Novel #Orthohantavirus Associated with #Hantavirus Pulmonary Syndrome in Northern #Argentina

Abstract

In this work, we performed the genetic characterization of a new variant of orthohantavirus associated with a fatal case of hantavirus pulmonary syndrome, outside the known endemic region, in northwestern Argentina. We first confirmed an orthohantavirus infection by ELISA, testing for the detection of IgM and IgG antibodies. Then, we extracted RNA from 100 microliters of serum, the only sample available, followed by RT-PCR. The amplicons were sequenced using Sanger and next-generation sequencing technology. We obtained partial sequences of 1253 bp, 799 bp and 1675 bp from the S-, M- and L-segments, respectively, showing low sequence identities with all the previously characterized hantaviruses (10.9%, 13.5% and 15.1% of the divergence, respectively). The phylogenetic analysis showed that this virus belongs to the Orthohantavirus andesense species (ANDV), and among the ANDV-like variants, it is more closely related to the Lechiguanas clade. Similar percentages of divergence were considered sufficient to distinguish AND-like variants in previous works. As the patient had no travel history before the onset of disease was reported, we conducted rodent surveys to confirm the presence of reservoirs. The rodent assemblage was compatible with the transitional zone among different ecoregions (Yungas, Chaco and Monte). Moreover, one of the species captured, Oligoryzomys flavescens, was previously described as a reservoir of hantavirus. This species may either host several variants across its range or encompass a species complex, as proposed by some authors.

Source: Viruses, https://www.mdpi.com/1999-4915/17/5/717

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#Argentina - #Influenza A #H5 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

National Service of Agri-Food Health and Quality (SENASA) received a notification concerning a high mortality of birds and signs consistent with high pathogenicity avian influenza (HPAI) in a backyard. The suspicion was immediately addressed and samples were taken for analysis. The samples tested positive for HPAI H5. The affected species are chickens, ducks and turkeys. The affected premises are adjacent to a body of water, so contact with wild birds is presumed. Stamping out, sanitary burial, cleaning and disinfection of all the birds in the premises will be carried out. We will update the quantitative data in subsequent follow-up reports.

Source: WOAH, https://wahis.woah.org/#/in-review/6272

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#Pathology of #Influenza A (#H5N1) #infection in #pinnipeds reveals novel tissue #tropism and vertical #transmission.

Abstract

In 2023, an unprecedented outbreak of highly pathogenic avian influenza (HPAI) H5N1 resulted in the death of thousands of pinnipeds along the Argentinean coast, raising concerns about its ecological and epidemiological impact. Here, we present clinical, pathological, and molecular findings associated with HPAI H5N1 infection in pinnipeds from Chubut, Argentina. Necropsies were conducted on three South American Sea Lions (SASLs) (Otaria flavescens) and one Southern Elephant Seal (SES) (Mirounga leonina), followed by histopathological, immunohistochemical and RT-sqPCR analyses. Neurological clinical signs were observed in two SASLs, with one also exhibiting respiratory distress. Neuropathological findings included lymphoneutrophilic meningoencephalomyelitis and choroiditis, neuronal necrosis, gliosis, hemorrhages, and perivascular cuffing. Viral antigen was localized in neurons, glial cells, choroid plexus epithelial cells, ependymal cells, and the neuropil. Systemic manifestations included HPAI-related necrotizing myocarditis in the elephant seal and placental necrosis in a sea lion, with fetal tissues testing positive for HPAIV. Pulmonary lesions were minimal, limited to bronchial glands in one individual. RT-sqPCR confirmed HPAI H5 in all tested animals. Our findings highlight the neurotropism of HPAI H5N1 in pinnipeds, and expand the known systemic effects of the virus, revealing new tissue tropism and vertical transmission.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.02.07.636856v1

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#Bussuquara Virus: A Neglected #Orthoflavivirus with Broad Distribution Across Central and South #America and the #Caribbean

Abstract

Bussuquara virus (BSQV) was first discovered in the Brazilian Amazon in 1956. It is an arthropod-borne virus (arbovirus) in the genus Orthoflavivirus, family Flaviviridae. Since its discovery, BSQV has been sporadically detected across the South (Brazil, Columbia, and Argentina) and Central (Panama and Mexico) America and the Caribbean (Grenada), but there is minimal BSQV surveillance due to limited public health awareness and a lack of specific or sensitive diagnostics. BSQV exposure has been reported in a wide range of host and vector species, including humans. Little information is available in the literature and herein we summarize the published historical findings on BSQV and suggest a pathway for future studies to better understand its potential emergence into human populations.

Source: Viruses, https://www.mdpi.com/1999-4915/17/2/183

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