 It has been determined that the strain contains genes from five different flu viruses : North American swine influenza , North American avian influenza , human influenza and two swine influenza viruses typically found in Asia and Europe . Further analysis has shown that several proteins of the virus are most similar to strains that cause mild symptoms in humans , leading virologist Wendy Barclay to suggest on 1 May 2009 , that the initial indications are that the virus was unlikely to cause severe symptoms for most people . 
