Hepatitis C is an infection caused by a virus that attacks the liver and leads to inflammation. Most people infected with the hepatitis C virus (HCV) have no symptoms. In fact, most people don't know they have the hepatitis C infection until liver damage shows up, decades later, during routine medical tests. Hepatitis C is one of several hepatitis viruses and is generally considered to be among the most serious of these viruses. Hepatitis C is passed through contact with contaminated blood - most commonly through needles shared during illegal drug use. Hepatitis C infection usually produces no signs or symptoms during its earliest stages. When signs and symptoms do occur, they're generally mild and flu-like and may include: Fatigue; Fever; Nausea or poor appetite; Muscle and joint pains; Tenderness in the area of your liver