RESUMO
Swine influenza A viruses (SwIV) cause significant economic losses in animal husbandry as well as instances of human disease and occasionally give rise to human pandemics, including that caused by the H1N1/2009 virus. The lack of systematic and longitudinal influenza surveillance in pigs has hampered attempts to reconstruct the origins of this pandemic. Most existing swine data were derived from opportunistic samples collected from diseased pigs in disparate geographical regions, not from prospective studies in defined locations, hence the evolutionary and transmission dynamics of SwIV are poorly understood. Here we quantify the epidemiological, genetic and antigenic dynamics of SwIV in Hong Kong using a data set of more than 650 SwIV isolates and more than 800 swine sera from 12 years of systematic surveillance in this region, supplemented with data stretching back 34 years. Intercontinental virus movement has led to reassortment and lineage replacement, creating an antigenically and genetically diverse virus population whose dynamics are quantitatively different from those previously observed for human influenza viruses. Our findings indicate that increased antigenic drift is associated with reassortment events and offer insights into the emergence of influenza viruses with epidemic potential in swine and humans.
Assuntos
Evolução Molecular , Vírus da Influenza A Subtipo H1N1/fisiologia , Infecções por Orthomyxoviridae/veterinária , Doenças dos Suínos/transmissão , Doenças dos Suínos/virologia , Suínos/virologia , Zoonoses/virologia , Animais , Aves/virologia , Feminino , Hong Kong/epidemiologia , Humanos , Vírus da Influenza A Subtipo H1N1/classificação , Vírus da Influenza A Subtipo H1N1/genética , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Influenza Aviária/transmissão , Influenza Aviária/virologia , Influenza Humana/epidemiologia , Influenza Humana/transmissão , Influenza Humana/virologia , Masculino , Epidemiologia Molecular , Dados de Sequência Molecular , Infecções por Orthomyxoviridae/epidemiologia , Infecções por Orthomyxoviridae/transmissão , Infecções por Orthomyxoviridae/virologia , Filogenia , Vigilância da População , Vírus Reordenados/genética , Vírus Reordenados/imunologia , Vírus Reordenados/isolamento & purificação , Vírus Reordenados/fisiologia , Suínos/sangue , Doenças dos Suínos/sangue , Doenças dos Suínos/epidemiologia , Zoonoses/epidemiologia , Zoonoses/transmissãoRESUMO
After multiple discrete introductions of influenza A(H1N1)pdm09 virus into Sri Lanka, the virus was transmitted among humans, then swine. The spread of virus between geographically distant swine farms is consistent with virus dispersal associated with a vehicle used for swine transportation, although this remains unproven.
Assuntos
Vírus da Influenza A Subtipo H1N1/classificação , Vírus da Influenza A Subtipo H1N1/genética , Influenza Humana/epidemiologia , Infecções por Orthomyxoviridae/veterinária , Doenças dos Suínos/epidemiologia , Animais , Humanos , Influenza Humana/virologia , Dados de Sequência Molecular , Infecções por Orthomyxoviridae/epidemiologia , Infecções por Orthomyxoviridae/virologia , Filogenia , Filogeografia , RNA Viral , Sri Lanka/epidemiologia , Suínos , Doenças dos Suínos/virologiaRESUMO
To study influenza viruses in pigs in Sri Lanka, we examined samples from pigs at slaughterhouses. Influenza (H3N2) and A(H1N1)pdm09 viruses were prevalent during 2004-2005 and 2009-2012, respectively. Genetic and epidemiologic analyses of human and swine influenza viruses indicated 2 events of A(H1N1)pdm09 virus spillover from humans to pigs.
Assuntos
Infecções por Orthomyxoviridae/veterinária , Infecções Respiratórias/veterinária , Doenças dos Suínos/virologia , Matadouros , Animais , Linhagem Celular , Embrião de Galinha , Cães , Humanos , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Vírus da Influenza A Subtipo H3N2/isolamento & purificação , Infecções por Orthomyxoviridae/epidemiologia , Infecções por Orthomyxoviridae/virologia , Filogenia , Prevalência , Infecções Respiratórias/epidemiologia , Infecções Respiratórias/virologia , Estudos Soroepidemiológicos , Sri Lanka/epidemiologia , Sus scrofa/virologia , Suínos/virologia , Doenças dos Suínos/epidemiologiaRESUMO
South Asia has experienced regular outbreaks of H5N1 avian influenza virus since its first detection in India and Pakistan in February, 2006. Till 2009, the outbreaks in this region were due to clade 2.2 H5N1 virus. In 2010, Nepal reported the first outbreak of clade 2.3.2 virus in South Asia. In February 2011, two outbreaks of H5N1 virus were reported in the State of Tripura in India. The antigenic and genetic analyses of seven H5N1 viruses isolated during these outbreaks were carried out. Antigenic analysis confirmed 64 to 256-fold reduction in cross reactivity compared with clade 2.2 viruses. The intravenous pathogenicity index of the isolates ranged from 2.80-2.95 indicating high pathogenicity to chickens. Sequencing of all the eight gene-segments of seven H5N1 viruses isolated in these outbreaks was carried out. The predicted amino acid sequence analysis revealed high pathogenicity to chickens and susceptibility to the antivirals, amantadine and oseltamivir. Phylogenetic analyses indicated that these viruses belong to clade 2.3.2.1 and were distinct to the clade 2.3.2.1 viruses isolated in Nepal. Identification of new clade 2.3.2 H5N1 viruses in South Asia is reminiscent of the introduction of clade 2.2 viruses in this region in 2006/7. It is now important to monitor whether the clade 2.3.2.1 is replacing clade 2.2 in this region or co-circulating with it. Continued co-circulation of various subclades of the H5N1 virus which are more adapted to land based poultry in a highly populated region such as South Asia increases the risk of evolution of pandemic H5N1 strains.