title: What is the true nature of epidemic influenza virus and how do new epidemic viruses spread?
mesh_terms: D000818:Animals; D004196:Disease Outbreaks; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission*; D009975:Orthomyxoviridae / Q000254:growth & development / Q000276:immunology*