During November 2010, Wisconsin Division of Public Health (DPH) staff members noted the number of hepatitis C virus (HCV) infections reported annually among persons aged <30 years in six contiguous rural counties of Wisconsin had increased from an average of eight cases per year during 2004-2008 to an average of 24 cases per year during 2009-2010. To understand factors associated with this increase, DPH, local health departments, and CDC investigated the epidemiologic and laboratory characteristics of 25 cases reported during 2010 among adults aged <30 years who resided in these six counties.