RESUMEN
Clade 2.3.4.4b highly pathogenic avian influenza (HPAI) H5N1 virus was detected in the South American sea lions found dead in Santa Catarina, Brazil, in October 2023. Whole genome sequencing and comparative phylogenetic analysis were conducted to investigate the origin, genetic diversity, and zoonotic potentials of the H5N1 viruses. The H5N1 viruses belonged to the genotype B3.2 of clade 2.3.4.4b H5N1 virus, which was identified in North America and disseminated to South America. They have acquired new amino acid substitutions related to mammalian host affinity. Our study provides insights into the genetic landscape of HPAI H5N1 viruses in Brazil, highlighting the continuous evolutionary processes contributing to their possible adaptation to mammalian hosts.
Asunto(s)
Subtipo H5N1 del Virus de la Influenza A , Filogenia , Leones Marinos , Secuenciación Completa del Genoma , Animales , Leones Marinos/virología , Brasil , Subtipo H5N1 del Virus de la Influenza A/genética , Subtipo H5N1 del Virus de la Influenza A/clasificación , Infecciones por Orthomyxoviridae/veterinaria , Infecciones por Orthomyxoviridae/virología , Genoma Viral , Genotipo , Variación GenéticaRESUMEN
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.
Asunto(s)
Brotes de Enfermedades , Subtipo H5N1 del Virus de la Influenza A , Gripe Aviar , Filogenia , Filogeografía , Animales , Brasil/epidemiología , Gripe Aviar/virología , Gripe Aviar/epidemiología , Subtipo H5N1 del Virus de la Influenza A/genética , Subtipo H5N1 del Virus de la Influenza A/clasificación , Subtipo H5N1 del Virus de la Influenza A/aislamiento & purificación , Aves/virología , Mamíferos/virología , Aves de Corral/virología , Humanos , Genotipo , Neuraminidasa/genética , Proteínas Virales/genética , Mutación , Animales Salvajes/virologíaRESUMEN
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.
Asunto(s)
Hurones , Subtipo H5N1 del Virus de la Influenza A , Gripe Humana , Infecciones por Orthomyxoviridae , Animales , Hurones/virología , Humanos , Chile , Gripe Humana/virología , Gripe Humana/transmisión , Infecciones por Orthomyxoviridae/virología , Infecciones por Orthomyxoviridae/transmisión , Infecciones por Orthomyxoviridae/veterinaria , Subtipo H5N1 del Virus de la Influenza A/genética , Subtipo H5N1 del Virus de la Influenza A/patogenicidad , Subtipo H5N1 del Virus de la Influenza A/aislamiento & purificación , Subtipo H5N1 del Virus de la Influenza A/clasificación , Subtipo H5N1 del Virus de la Influenza A/fisiología , Virus Reordenados/genética , Virus Reordenados/aislamiento & purificación , Virus Reordenados/patogenicidad , Virus Reordenados/clasificación , Filogenia , Gripe Aviar/virología , Gripe Aviar/transmisiónRESUMEN
PURPOSE OF REVIEW: Data on influenza in tropical countries remain scarce compared with that in temperate countries. However, the emergence of avian influenza virus (H5N1) and the 2009 pandemic represented a major stimulus for advances in knowledge about influenza in many of these countries. This review summarizes recent data on viral and epidemiologic aspects of the condition in tropical countries. RECENT FINDINGS: Avian influenza and the influenza pandemic of 2009 have contributed to pioneer production of data on influenza in the tropical settings. Preliminary data on epidemiology, genetic diversity, and antiviral resistance of influenza viruses (seasonal and pandemic) in tropical countries have been published recently. SUMMARY: The seasonality of influenza is very diverse in tropical countries. Recent studies on the subject confirm the year-round activity of these viruses in many countries and the regular occurrence of epidemic outbreaks in others. The use of molecular diagnostic methods has led to prevalence rates comparable to those seen in temperate countries. Phylogenetic analysis of hemagglutinin of influenza isolates allows understanding of the evolution and divergence of avian (H5N1) and human influenza viruses (A/H1N1, A/H3N2, and B) in tropical settings. Influenza viruses resistant to oseltamivir and zanamivir have been detected in tropical countries despite the rare use of these drugs in the treatment of influenza in people living in these areas.