Swine influenza viruses (SIVs) are respiratory pathogens of pigs. They cause both economic bur den in livestock-dependent industries and serious global public health concerns in humans. Because of their dual susceptibility to human and avian influenza viruses, pigs are recognized as intermediate hosts for genetic reassortment and interspecies transmission. Subtypes H1N1, H1N2, and H3N2 circulate in swine populations around the world, with varied origin and genetic characteristics among different continents and regions. In this review, the role of pigs in evolution of influenza A viruses, the genetic evolution of SIVs and interspecies transmission of SIVs are described. Considering the possibility that pigs might produce novel influenza viruses causing more outbreaks and pandemics, routine epidemiological surveillance of influenza viruses in pig populations is highly recommended.
Animals ; Humans ; Influenza A virus ; genetics ; isolation & purification ; physiology ; Influenza, Human ; epidemiology ; transmission ; virology ; Orthomyxoviridae Infections ; epidemiology ; transmission ; veterinary ; virology ; Swine ; Swine Diseases ; epidemiology ; transmission ; virology

Most isolates of foot-and-mouth disease virus (FMDV) display a broad host range. Since the late 1990s, the genetic lineage of PanAsia topotype FMDV serotype O has caused epidemics in the Far East, Africa, the United Kingdom, France, the Netherlands, and numerous other countries throughout Europe and Asia. In contrast, there are several FMDV isolates that exhibit a more restricted host range. A Cathay topotype isolate of FMDV serotype O from the 1997 epizootic in Taiwan (O/TAW/97) demonstrated restricted host specificity, only infecting swine. Methods used to evaluate infectivity and pathogenicity of FMDV isolates in cattle are well-documented, but there has been less progress studying transmission and pathogenicity of FMDV isolates in pigs. In previous studies designed to examine pathogenicity, various chimeric viruses derived from O/TAW/97 were intradermally inoculated in the heel bulb of pigs. Subsequent quantitative scoring of disease and evaluation of virus released into nasal secretions and blood was assessed. Here we prove the usefulness of this method in direct and contact inoculated pigs to evaluate infectivity, pathogenicity and transmission of different Asian FMDV isolates. Virus strains within the Cathay topotype were highly virulent in swine producing a synchronous disease in inoculated animals and were efficiently spread to in-contact naive pigs, while virus strains from the PanAsia topotype displayed more heterogeneous properties.
Animals ; Antibodies, Viral/blood ; Disease Outbreaks/*veterinary ; Foot-and-Mouth Disease/epidemiology/transmission/*virology ; Foot-and-Mouth Disease Virus/*pathogenicity ; Host Specificity ; Swine ; Swine Diseases/epidemiology/transmission/*virology ; Taiwan/epidemiology

Since the first report of a swine influenza virus (SIV) infection in humans in 1958, cases have occurred continuously and increased significantly after the 2009 H1N1 pandemic. Although exposure to swine is thought to be a risk factor for human SIVs infections, approximately half of the reported cases had no known exposure to pigs. Besides, epidemiological investigation showed that several cases had limited human-to-human transmission. Based on the analyses of data on swine influenza virus infection in humans in this review, both the improved SIVs surveillance in humans and swine population and wider vaccination coverage among occupational workers are critical strategies in pandemic preparedness and response.
Animals ; Humans ; Influenza A virus ; genetics ; isolation & purification ; physiology ; Influenza, Human ; diagnosis ; epidemiology ; transmission ; virology ; Orthomyxoviridae Infections ; diagnosis ; epidemiology ; veterinary ; virology ; Swine ; Swine Diseases ; diagnosis ; epidemiology ; transmission ; virology ; Zoonoses ; diagnosis ; epidemiology ; transmission ; virology