The Daily Republic, Mitchell, S.D. Some wonderful news: Flu season is almost over. Oh, what a relief that is. The bad news? South Dakota health officials have been fighting a record number of flu cases during the 2014-15 flu season, which runs from early October to mid-May. According to figures from the South Dakota Department of Health, 58 South Dakotans died and 731 people were hospitalized with influenza this season.