Fortalecimiento de la planificación de la preparación para pandemias causadas por agentes patógenos respiratorios: Sinopsis de política, 27 de abril del 2022

Atendiendo a las resoluciones WHA58.5 y WHA74.7, la Organización Mundial de la Salud (OMS) se ha comprometido a brindar apoyo a los Estados Miembros en la planificación de la preparación para pandemias mediante la prestación de orientación y asistencia técnica. Esta sinopsis de política responde a las solicitudes nacionales y regionales de un enfoque integrado de la preparación para pandemias causadas por agentes patógenos respiratorios que esté en consonancia con el Reglamento Sanitario Internacional (2005) (RSI) y las orientaciones de la OMS relativas a la preparación de la respuesta nacional frente a emergencias de salud y desastres. En esta sinopsis de política se presentan los elementos fundamentales con los que se alienta a los Estados Miembros a: a) formular un enfoque integrado para la planificación de la preparación para pandemias causadas por agentes patógenos respiratorios y b) mejorar las capacidades funcionales subnacionales y nacionales para la preparación. Además, se destacan las medidas recomendadas a los Estados Miembros cuando estos inician o actualizan el proceso de planificación de la preparación para una pandemia a nivel subnacional y nacional. La sinopsis sirve para brindar a los Estados Miembros y a los asociados un fundamento y una orientación sobre estos elementos básicos y las medidas recomendadas, al tiempo que la OMS colabora con ellos en la elaboración de un conjunto de recursos para pandemias causadas por agentes patógenos respiratorios, un repositorio virtual de materiales sobre la planificación de la preparación para las partes interesadas nacionales, regionales y mundiales. La planificación de la preparación para pandemias causadas por agentes patógenos respiratorios permite a los Estados Miembros formular planes en relación con los aspectos que son comunes a los agentes patógenos con una vía de transmisión respiratoria, tanto ya conocidos como nuevos. En consonancia con el plan estratégico de preparación, disposición operativa y respuesta para poner fin a la emergencia mundial causada por la COVID-19 para el 2022, la OMS alienta a los Estados Miembros a considerar un enfoque integrado de la planificación de la preparación frente a los agentes patógenos respiratorios que se ajuste a sus procesos de planificación nacional y ciclos presupuestarios existentes

Infection of South American coatis (Nasua nasua) with highly pathogenic avian influenza H5N1 virus displaying mammalian adaptive mutations.

Deadly outbreaks among poultry, wild birds, and carnivorous mammals by the highly pathogenic H5N1 virus of the clade 2.3.4.4b have been reported in South America. The increasing virus incidence in various mammal species poses a severe zoonotic and pandemic threat. In Uruguay, the clade 2.3.4.4b viruses were first detected in February 2023, affecting wild birds and backyard poultry. Three months after the first reported case in Uruguay, the disease affected a population of 23 coatis (Nasua) in an ecological park. Most animals became infected, likely directly or indirectly from wild birds in the park, and experienced sudden death. Five animals from the colony survived, and four of them developed antibodies. The genomes of the H5N1 strains infecting coatis belonged to the B3.2 genotype of the clade 2.3.4.4b. Genomes from coatis were closely associated with those infecting backyard poultry, but transmission likely occurred through wild birds. Notable, two genomes have a 627K substitution in the RNA polymerase PB2 subunit, a hallmark amino acid linked to mammalian adaptation. Our findings support the ability of the avian influenza virus of the 2.3.4.4b clade to infect and transmit among terrestrial mammals with high pathogenicity and undergo rapid adaptive changes. It also highlights the coatis' ability to develop immunity and naturally clear the infection.

Risk for Waterborne Transmission and Environmental Persistence of Avian Influenza Virus in a Wildlife/Domestic Interface in Mexico.

Aquatic habitats provide a bridge for influenza transmission among wild and domestic species. However, water sources pose highly variable physicochemical and ecological characteristics that affect avian influenza virus (AIV) stability. Therefore, the risk of survival or transmissibility of AIV in the environment is quite variable and has been understudied. In this study, we determine the risk of waterborne transmission and environmental persistence of AIV in a wild/domestic bird interface in the Central Mexico plateau (North America) during the winter season using a multi-criteria decision analysis (MCDA). A total of 13 eco-epidemiological factors were selected from public-access databases to develop the risk assessment. The MCDA showed that the Atarasquillo wetland presents a higher persistence risk in January. Likewise, most of the backyard poultry farms at this wild-domestic interface present a high persistence risk (50%). Our results suggest that drinking water may represent a more enabling environment for AIV persistence in contrast with wastewater. Moreover, almost all backyard poultry farms evidence a moderate or high risk of waterborne transmission especially farms close to water bodies. The wildlife/domestic bird interface on the Atarasquillo wetland holds eco-epidemiological factors such as the presence of farms in flood-prone areas, the poultry access to outdoor water, and the use of drinking-water troughs among multiple animal species that may enhance waterborne transmission of AIV. These findings highlight the relevance of understanding the influence of multiple factors on AIV ecology for early intervention and long-term control strategies.

Phylodynamics of avian influenza A(H5N1) viruses from outbreaks in Brazil.

Our study identified strains of the A/H5N1 virus in analyzed samples of subsistence poultry, wild birds, and mammals, belonging to clade 2.3.4.4b, genotype B3.2, with very high genetic similarity to strains from Chile, Uruguay, and Argentina. This suggests a migratory route for wild birds across the Pacific, explaining the phylogenetic relatedness. The Brazilian samples displayed similarity to strains that had already been previously detected in South America. Phylogeographic analysis suggests transmission of US viruses from Europe and Asia, co-circulating with other lineages in the American continent. As mutations can influence virulence and host specificity, genomic surveillance is essential to detect those changes, especially in critical regions, such as hot spots in the HA, NA, and PB2 sequences. Mutations in the PB2 gene (D701N and Q591K) associated with adaptation and transmission in mammals were detected suggesting a potential zoonotic risk. Nonetheless, resistance to neuraminidase inhibitors (NAIs) was not identified, however, continued surveillance is crucial to detect potential resistance. Our study also mapped the spread of the virus in the Southern hemisphere, identifying possible entry routes and highlighting the importance of surveillance to prevent outbreaks and protect both human and animal populations.

Stranding and mass mortality in humboldt penguins (Spheniscus humboldti), associated to HPAIV H5N1 outbreak in Chile.

The highly pathogenic Avian Influenza virus (HPAIV) H5N1 has caused a global outbreak affecting both wild and domestic animals, predominantly avian species. To date, cases of the HPAIV H5 Clade 2.3.4.4b in penguins have exclusively been reported in African Penguins. In Chile, the virus was confirmed in pelicans in December 2022 and subsequently spread across the country, affecting several species, including Humboldt penguins. This study aims to provide an overview of the incidents involving stranded and deceased Humboldt penguins and establish a connection between these events and HPAIV H5N1. Historical data about strandings between 2009 and 2023 was collected, and samples from suspected cases in 2023 were obtained to confirm the presence of HPAIV H5N1. Between January and August 2023, 2,788 cases of stranded and deceased penguins were recorded. Out of these, a total of 2,712 penguins deceased, evidencing a significative increase in mortality starting in early 2023 coinciding with the introduction and spreading of HPAIV H5N1 in the country. Thirty-seven events were categorized as mass mortality events, with the number of deceased penguins varying from 11 to 98. Most cases (97 %) were observed in the North of Chile. One hundred and eighty-one specimens were subjected to HPAIV diagnosis, four of which tested positive for HPAIV H5N1. Spatial analysis validates the correlation between mass mortality events and outbreaks of HPAIV in Chile. However, the limited rate of HPAIV H5N1 detection, which can be attributed to the type and quality of the samples, requiring further exploration.

Evidence of reassortment of avian influenza A (H2) viruses in Brazilian shorebirds.

Influenza A viruses of the H2 subtype represent a zoonotic and pandemic threat to humans due to a lack of widespread specific immunity. Although A(H2) viruses that circulate in wild bird reservoirs are distinct from the 1957 pandemic A(H2N2) viruses, there is concern that they could impact animal and public health. There is limited information on AIVs in Latin America, and next to nothing about H2 subtypes in Brazil. In the present study, we report the occurrence and genomic sequences of two influenza A viruses isolated from wild-caught white-rumped sandpipers (Calidris fuscicollis). One virus, identified as A(H2N1), was isolated from a bird captured in Restinga de Jurubatiba National Park (PNRJ, Rio de Janeiro), while the other, identified as A(H2N2), was isolated from a bird captured in Lagoa do Peixe National Park (PNLP, Rio Grande do Sul). DNA sequencing and phylogenetic analysis of the obtained sequences revealed that each virus belonged to distinct subtypes. Furthermore, the phylogenetic analysis indicated that the genomic sequence of the A(H2N1) virus isolated from PNRJ was most closely related to other A(H2N1) viruses isolated from North American birds. On the other hand, the A(H2N2) virus genome recovered from the PNLP-captured bird exhibited a more diverse origin, with some sequences closely related to viruses from Iceland and North America, and others showing similarity to virus sequences recovered from birds in South America. Viral genes of diverse origins were identified in one of the viruses, indicating local reassortment. This suggests that the extreme South of Brazil may serve as an environment conducive to reassortment between avian influenza virus lineages from North and South America, potentially contributing to an increase in overall viral diversity.

Pacific and Atlantic sea lion mortality caused by highly pathogenic Avian Influenza A(H5N1) in South America.

We describe the evolution of the outbreak of Highly Pathogenic Avian Influenza (HPAI) A(H5N1) in sea lions (Otaria flavescens) of South America. At least 24,000 sea lions died in Peru, Chile, Argentina, Uruguay, and Brazil between January-October 2023. The most plausible route of infection is cohabiting with or foraging on infected birds. However, we urge a detailed evaluation of the sea lions actual source of infection given that the concomitant massive wild bird mortalities registered in the Pacific Ocean did not occur in the Atlantic Ocean.

Highly pathogenic avian influenza A(H5N1) virus of clade 2.3.4.4b isolated from a human case in Chile causes fatal disease and transmits between co-housed ferrets.

Clade 2.3.4.4b highly pathogenic avian influenza A(H5N1) viruses have caused large outbreaks within avian populations on five continents, with concurrent spillover into a variety of mammalian species. Mutations associated with mammalian adaptation have been sporadically identified in avian isolates, and more frequently among mammalian isolates following infection. Reports of human infection with A(H5N1) viruses following contact with infected wildlife have been reported on multiple continents, highlighting the need for pandemic risk assessment of these viruses. In this study, the pathogenicity and transmissibility of A/Chile/25945/2023 HPAI A(H5N1) virus, a novel reassortant with four gene segments (PB1, PB2, NP, MP) from North American lineage, isolated from a severe human case in Chile, was evaluated in vitro and using the ferret model. This virus possessed a high capacity to cause fatal disease, characterized by high morbidity and extrapulmonary spread in virus-inoculated ferrets. The virus was capable of transmission to naïve contacts in a direct contact setting, with contact animals similarly exhibiting severe disease, but did not exhibit productive transmission in respiratory droplet or fomite transmission models. Our results indicate that the virus would need to acquire an airborne transmissible phenotype in mammals to potentially cause a pandemic. Nonetheless, this work warrants continuous monitoring of mammalian adaptations in avian viruses, especially in strains isolated from humans, to aid pandemic preparedness efforts.

Highly pathogenic avian influenza virus H5N1 clade 2.3.4.4b from Peru forms a monophyletic group with Chilean isolates in South America.

Highly pathogenic avian Influenza virus (HPAIV) has spread in an unprecedented extent globally in recent years. Despite the large reports of cases in Asia, Europe, and North America, little is known about its circulation in South America. Here, we describe the isolation, and whole genome characterization of HPAIV obtained from sampling 26 wild bird species in Peru, representing one of the largest studies in our region following the latest HPAIV introduction in South America. Out of 147 samples analyzed, 22 were positive for detection of avian influenza virus using a qRT-PCR-based assay. Following inoculation into embryonated chicken eggs, fourteen viral isolates were obtained from which nine isolates were selected for genome characterization, based on their host relevance. Our results identified the presence of HPAIV H5N1 subtype in a highly diverse wild bird species. Phylogenetic analysis revealed that these isolates correspond to the clade 2.3.4.4b, sharing a common ancestor with North American isolates and forming a monophyletic group along with isolates from Chile. Altogether, changes at the amino acid levels compared to their closest relatives indicates the virus is evolving locally, highlighting the need for constant genomic surveillance. This data evidence the chances for spillover events increases as the virus spreads into large populations of immunologically naïve avian species and adding conditions for cross species transmission.

Highly Pathogenic Avian Influenza A(H5N1) Viruses from Multispecies Outbreak, Argentina, August 2023.

We report full-genome characterization of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus from an outbreak among sea lions (August 2023) in Argentina and possible spillover to fur seals and terns. Mammalian adaptation mutations in virus isolated from marine mammals and a human in Chile were detected in mammalian and avian hosts.

Incursion of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus, Brazil, 2023.

We report 4 highly pathogenic avian influenza A(H5N1) clade 2.3.4.4.b viruses in samples collected during June 2023 from Royal terns and Cabot's terns in Brazil. Phylodynamic analysis revealed viral movement from Peru to Brazil, indicating a concerning spread of this clade along the Atlantic Americas migratory bird flyway.

A perspective of the prevalent H9N2 virus with a special focus on molecular and pathological aspects in commercial broiler chicken in Punjab, Pakistan / Perspectiva do vírus H9N2 prevalente com foco especial em aspectos moleculares e patológicos em frangos de corte comerciais em Punjab, Paquistão

Frequent outbreaks of avian influenza H9N2 virus in Pakistan revealed that this subtype has become endemic in the poultry industry and, besides economic losses, poses a threat to public health. The present study describes the molecular characterization and pathological alterations in naturally infected broiler chickens with the current H9N2 field strain and their phylogenomic dynamics. In this study, tissue samples (trachea, lung, kidney and intestine) from 100 commercial chicken flocks were collected from July 2018 to August 2019. Samples were subjected to molecular detection, phylogeny and subsequent pathological examination. The complete length of the HA gene was successfully amplified in five samples. Nucleotide sequencing revealed positive samples placed in a clade belonging to the B2 sub-lineage of the G1 genotype and categorized as LPAIV based on the amino acid sequence of the HA gene at the cleavage site (PAKSSR/G). Genetic analysis of the haemagglutinin (HA) gene revealed nt: 80.5%-99.5%; aa: 83.8%-98.9% homology to H9N2 strains reported previously from Pakistan, neighbouring countries, and (A/Quail/Hong Kong/G1/97). Gross lesions include a slight airsacculitis, mild hemorrhages, diffuse congestion and purulent exudate in tracheal mucosa, fibrinonecrotic cast in the trachea lumen and mild pulmonary congestion. Histopathological alterations include sloughing of epithelial cells and infiltration of inflammatory cells in the trachea, mononuclear cells (MNCs) infiltration, pulmonary congestion and exudate in the lumen of parabronchi, peritubular congestion in the kidneys with degeneration of tubular epithelial cells and degenerative changes in the intestinal villi epithelial cells and goblet cell hyperplasia. Immunohistochemistry analysis confirmed the presence of AIVH9N2 antigen in the trachea, lungs, kidney and intestine. Electron microscopy revealed ultrastructural changes in the trachea, including degenerated cilia, mitochondrial swelling and enlarged endoplasmic reticulum. Based on all essential analysis, the present study revealed the distribution of the H9N2 virus of G1 genotype in Punjab, Pakistan, with mild to moderate pathogenicity.

Surtos frequentes do vírus da gripe aviária H9N2 no Paquistão revelaram que esse subtipo se tornou endêmico na avicultura e, além das perdas econômicas, representa uma ameaça à saúde pública. O presente estudo descreve a caracterização molecular e as alterações patológicas em frangos de corte naturalmente infectados com a atual cepa H9N2 e sua dinâmica filogenômica. Neste estudo, amostras de tecidos (traqueia, pulmões, rim e intestino) de 100 lotes comerciais de frangos foram coletadas de julho de 2018 a agosto de 2019. As amostras foram submetidas à detecção molecular, filogenia e posterior exame patológico. O comprimento completo do gene HA foi amplificado com sucesso em cinco amostras. O sequenciamento de nucleotídeos revelou amostras positivas colocadas em um clado pertencente à sublinhagem B2 do genótipo G1 e categorizado como LPAIV com base na sequência de aminoácidos do gene da hemaglutinina (HA) no local de clivagem (PAKSSR/G). A análise genética do gene da HA revelou: nt = 80,5%-99,5%; aa = 83,8%-98,9% de homologia com cepas de H9N2 relatadas anteriormente no Paquistão e em países vizinhos (A/Quail/Hong Kong/G1/97). As lesões macroscópicas incluíram aerossaculite leve, hemorragias leves, congestão difusa e exsudato purulento na mucosa traqueal, cilindro fibrinonecrótico no lúmen da traqueia e congestão pulmonar leve. As alterações histopatológicas incluíram descamação de células epiteliais, infiltração de células inflamatórias na traqueia, infiltração de células mononucleares (MNCs), congestão pulmonar e exsudato no lúmen dos parabrônquios, congestão peritubular nos rins com degeneração das células epiteliais tubulares, alterações degenerativas nas células epiteliais das vilosidades intestinais e hiperplasia de células caliciformes. A análise imunoistoquímica confirmou a presença do antígeno AIVH9N2 na traqueia, nos pulmões, no rim e no intestino. A microscopia eletrônica revelou alterações ultraestruturais na traqueia, incluindo cílios degenerados, inchaço mitocondrial e retículo endoplasmático aumentado. Com base em todas as análises, o presente estudo revelou a distribuição do vírus H9N2 do genótipo G1 em Punjab, Paquistão, com patogenicidade de leve a moderada.

Boletín epidemiológico semana 1: Análisis del comportamiento de la tos ferina en Colombia a semana epidemiológica 52 de 2023. Influenza altamente patógena subtipo A (H5N1) / Epidemiological bulletin week 1: Analysis of the behavior of whooping cough in Colombia at epidemiological week 52 of 2023. Highly pathogenic influenza subtype A (H5N1)

La tos ferina es una enfermedad respiratoria altamente contagiosa causada por la bacteria Bordetella pertussis. Afecta principalmente a niños pequeños, pero también puede afectar a adolescentes y adultos. Se caracteriza por episodios severos de tos, que pueden terminar en un ruido agudo o "gallo" al inhalar. La tos ferina es particularmente peligrosa para los bebés menores de 6 meses, quienes aún no han completado el ciclo de vacunación. En 2020, la Organización Mundial de la Salud (OMS) reportó una incidencia global de 10 casos por cada 1 000 000 habitantes (69 552 casos), mientras que en el período 2021, se registró una incidencia de 4,6 casos por cada 1 000 habitantes (28 871 casos). La región de las Américas reportó 6 709 casos de tos ferina en 2021 y 3 283 casos de tos ferina en 2022 lo que representa una reducción del 104 % comparando estos dos años. La salud de las personas, los animales, las plantas y el medio ambiente están estrechamente interrelacionados. Los cambios en estas relaciones probablemente pueden aumentar el riesgo de que aparezcan y se propaguen nuevas enfermedades tanto en humanos como en animales. La OMS invita a que todos los países generen políticas públicas con el enfoque de «Una sola salud¼ con el fin de prevenir las enfermedades infecciosas. La influenza aviar es una enfermedad infecciosa que principalmente afecta a las aves (traspatio y silvestres), esta infección se da por el virus de la influenza aviar tipo A (familia Orthomyxoviridae). El nombre H5N1 se refiere al tipo de los antígenos de superficie presentes en el virus: hemaglutinina tipo 5 y neuraminidasa tipo 1. Las aves pueden infectarse por medio del contacto directo con aves acuáticas y de corral o a través del contacto con superficies contaminadas por el virus.

Whooping cough is a highly contagious respiratory disease caused by the bacteria Bordetella pertussis. It mainly affects children small, but it can also affect adolescents and adults. It is characterized by severe episodes of coughing, which may end in a noise sharp or "rooster" when inhaling. Whooping cough is particularly dangerous for Babies under 6 months, who have not yet completed the cycle of vaccination. In 2020, the World Health Organization (WHO) reported a global incidence of 10 cases per 1,000,000 inhabitants (69,552 cases), while in the 2021 period, an incidence of 4.6 cases per 1,000,000 inhabitants was recorded. every 1,000 inhabitants (28,871 cases). The Americas region reported 6,709 cases of whooping cough in 2021 and 3,283 cases of whooping cough in 2022 which represents a reduction of 104% comparing these two years. The health of people, animals, plants and the environment They are closely interrelated. The changes in these relationships They may probably increase the risk of new diseases emerging and spreading in both humans and animals. The OMS invites all countries to generate public policies with the focus of "One health" in order to prevent infectious diseases. Avian influenza is an infectious disease that mainly affects birds (backyard and wild). This infection is caused by the avian influenza virus type A (Orthomyxoviridae family). The name H5N1 refers to the type of surface antigens present on the virus: hemagglutinin type 5 and neuraminidase type 1. Birds can become infected through direct contact with waterfowl and poultry or through contact with surfaces contaminated by the virus.

Active surveillance for influenza virus and coronavirus infection in Antarctic birds and mammals in environmental fecal samples, South Shetland Islands.

Numerous Antarctic species are recognized as reservoirs for various pathogens, and their migratory behavior allows them to reach the Brazilian coast, potentially contributing to the emergence and circulation of new infectious diseases. To address the potential zoonotic risks, we conducted surveillance of influenza A virus (IAV) and coronaviruses (CoVs) in the Antarctic Peninsula, specifically focusing on different bird and mammal species in the region. During the summer of 2021/2022, as part of the Brazilian Antarctic Expedition, we collected and examined a total of 315 fecal samples to target these respiratory viruses. Although we did not detect the viruses of interest during this particular expedition, previous research conducted by our team has shown the presence of the H11N2 subtype of influenza A virus in penguin fecal samples from the same region. Given the continuous emergence of new viral strains worldwide, it is crucial to maintain active surveillance in the area, contributing to strengthening integrated One Health surveillance efforts.

Highly Pathogenic Avian Influenza A(H5N1) from Wild Birds, Poultry, and Mammals, Peru.

We identified highly pathogenic avian influenza A(H5N1) virus clade 2.3.4.4b in wild birds, poultry, and a lion in Peru during November 2022-February 2023 and markers associated with transmission adaptation and antiviral drug resistance. Continuous genomic surveillance is needed to inform public health measures and avoid mass animal deaths.

Mass mortality event in South American sea lions (Otaria flavescens) correlated to highly pathogenic avian influenza (HPAI) H5N1 outbreak in Chile.

In Chile, since January 2023, a sudden and pronounced increase in strandings and mortality has been observed among South American (SA) sea lions (Otaria flavescens), prompting significant concern. Simultaneously, an outbreak of highly pathogenic avian influenza H5N1 (HPAIV H5N1) in avian species has emerged since December 2022. To investigate the cause of this unexpected mortality, we conducted a comprehensive epidemiological and pathologic study. One hundred sixty-nine SA sea lions were sampled to ascertain their HPAIV H5N1 status, and long-term stranding trends from 2009 to 2023 were analyzed. In addition, two animals were necropsied. Remarkably, a significant surge in SA sea lion strandings was observed initiating in January 2023 and peaking in June 2023, with a count of 4,545 stranded and deceased animals. Notably, this surge in mortality correlates geographically with HPAIV outbreaks affecting wild birds. Among 168 sampled SA sea lions, 34 (20%) tested positive for Influenza A virus, and 21 confirmed for HPAIV H5N1 2.3.4.4b clade in tracheal/rectal swab pools. Clinical and pathological evaluations of the two necropsied stranded sea lions revealed prevalent neurological and respiratory signs, including disorientation, tremors, ataxia, and paralysis, as well as acute dyspnea, tachypnea, profuse nasal secretion, and abdominal breathing. The lesions identified in necropsied animals aligned with observed clinical signs. Detection of the virus via immunohistochemistry (IHC) and real-time PCR in the brain and lungs affirmed the findings. The findings provide evidence between the mass mortality occurrences in SA sea lions and HPAIV, strongly indicating a causal relationship. Further studies are needed to better understand the pathogenesis and transmission.

Deadly avian flu hits Galápagos.

Concerns rise for boobies, finches, and other endemic species.

Highly pathogenic avian influenza A (H5N1) in marine mammals and seabirds in Peru.

Highly pathogenic avian influenza (HPAI) A/H5N1 viruses (lineage 2.3.4.4b) are rapidly invading the Americas, threatening wildlife, poultry, and potentially evolving into the next global pandemic. In November 2022 HPAI arrived in Peru, triggering massive pelican and sea lion die-offs. We report genomic characterization of HPAI/H5N1 in five species of marine mammals and seabirds (dolphins, sea lions, sanderlings, pelicans and cormorants). Peruvian viruses belong to lineage 2.3.4.4b, but they are 4:4 reassortants where 4 genomic segments (PA, HA, NA and MP) position within the Eurasian lineage that initially entered North America from Eurasia, while the other 4 genomic segments (PB2, PB1, NP and NS) position within the American lineage (clade C) that circulated in North America. These viruses are rapidly accruing mutations, including mutations of concern, that warrant further examination and highlight an urgent need for active local surveillance to manage outbreaks and limit spillover into other species, including humans.

Spreading of the High-Pathogenicity Avian Influenza (H5N1) Virus of Clade 2.3.4.4b into Uruguay.

BACKGROUND: Avian influenza viruses (genus Alphainfluenzavirus, family Orthomyxoviridae) infect avian and mammal hosts. In 2022, the high pathogenicity avian influenza virus (H5N1) spread to South America, resulting in the loss of thousands of wild birds, including endangered species, and severely impacting the global poultry industry. OBJECTIVES: We analyzed the complete genomes of influenza viruses obtained from wild birds and backyard poultry in Uruguay between February and May 2023. METHODS: Twelve complete genomes were obtained in 2023 from cloacal swabs using Illumina sequencing. Genomes were phylogenetically analyzed with regional and global strains. FINDINGS: The identified strains have multiple basic amino acids at the hemagglutinin cleavage sites, which is typical for highly pathogenic strains. The Uruguayan viruses belonged to hemagglutinin clade 2.3.4.4b of the H5N1 subtype. A reassortment in North America has resulted in some segments of South American strains being of Eurasian or North American origins. The Uruguayan viruses shared a common ancestor with South American strains from Argentina and Chile. The influenza viruses displayed a spatiotemporal divergence pattern rather than being host-specific. MAIN CONCLUSIONS: The arrival of the 2.3.4.4b clade in Uruguay may have been mediated by birds that acquired the virus from Argentine and Chilean waterfowl migrating in the Pacific Flyway.