The Olsen laboratory studies influenza A viruses, which are medically and economically important human pathogens. Influenza A viruses also infect a variety of domestic and free-ranging wild animal species, including pigs, chickens, turkeys, horses, and marine mammals. Furthermore, influenza A virus infections in animals (especially in poultry, waterfowl, and pigs) play important roles in the development of pandemic human influenza viruses. The two primary focus areas in the lab currently are studies of the molecular epidemiology of animal influeza A viruses (especially swine viruses) and studies to determine the genetic factors that control interspecies transmission of influenza A viruses. The latter include research projects devoted to understanding human-to-swine influenza virus transmission, swine-to-human zoonotic influenza virus transmission, and transmission of viruses from birds to pigs and from pigs to birds.