Hepatitis C is of particular concern because an increasing number of people have been infected since the 1960's. Because many were unaware they were infected, the risks of transmitting the infection to others have been extremely high. Hepatitis C can be insidious, as frequently symptoms are mild or nonexistent when first acquired. Initially those who do have symptoms might feel like they have the "flu." For many, signs and symptoms appear only when liver disease is advanced and treatments are less effective. Most people with HCV infection develop chronic liver disease. Over the next 10-20 years the impact of HCV is expected to explode, as illness and deaths from HCV-related liver disease among the millions of people infected during earlier years will increase dramatically.