Illustration of the pig flu virus. The ca. 100nm big RNA virus is enveloped and belongs to the family of orthomyxoviridae. There are various subtypes of the influenza virus A, most of them belong to H1N1. Overall, they cause symptoms in several body systems (fever, lethargy, cough, cold, nausea, vomiting, diarrhea). The picture shows the formation of new virus variations, composed of viral genome of a human influenza virus as well as of a pig flu virus.