<prompt> Which of the following strain of influenza causes Swine flu which causes serious systemic manifestations?H1N1H5N1H3N1H3N3  <response>: Swine flu is caused by swine-origin H1N1 virus. Of the 15 HA subtypes found in birds, only a few have been transferred to mammals H1, H2, H3, and H5 in humans; H1 and H3 in swine; and H3 and H7 in horses. The same pattern holds for NA; nine NA subtypes are known for birds, only two of which are found in humans N1, N2. This pandemic strain of H1N1 causes a broad range of clinical symptoms ranging from typical symptoms fever, malaise, myalgias, cough, sore throat, rhinorrhea, shoness of breath commonly accompanied by gastrointestinal manifestations especially diarrhea to fulminant viral pneumonia. Ref: Brooks G.F., Carroll K.C., Butel J.S., Morse S.A., Mietzneron T.A. 2010. Chapter 39. Ohomyxoviruses Influenza Viruses. In G.F. Brooks, K.C. Carroll, J.S. Butel, S.A. Morse, T.A. Mietzneron Eds, Jawetz, Melnick, Adelbergs Medical Microbiology, 25e. 