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.