ABSTRACT

This chapter discusses the role swine play in the appearance of influenza viruses in humans, the pathology of swine-origin influenza viruses (SOIV) in humans as well as measures to control and prevent the emergence of SOIVs. Pigs have a unique position in the ecology of influenza. The epidemiology of influenza viruses in swine changed dramatically in 1997 when a human H3N2 virus was transmitted to pigs, thereby increasing the seroprevalence and isolation of H3N2 viruses from pigs. Influenza viruses continued to evolve and reassort in pigs with the appearance of an H1N2 isolate in Indiana in 1999. The picture of influenza in swine has become even more complex. With the continual introduction of genes from avian viruses, the swapping of genes between human seasonal influenza strains and swine lineages, the diversity of influenza viruses in pigs has increased dramatically. Human influenza infection causes a broad range of disease that varies from symptomless, mild infection, to severe respiratory illness.