Hepatitis C is one of several viruses that affect the liver. These copies of the virus go on to infect other liver cells. When the immune system attacks the infected cells, the liver becomes inflamed. This damages the liver and sometimes leads to cirrhosis - scarring of the liver. There are an estimated 4 million people infected with Hepatitis C in the United States.
Most new cases are among people who inject drugs.
Hepatitis C acts slowly - most people won't have any symptoms for 10 to 30 years after being infected. Most people with Hepatitis C develop some liver damage over time, though it's not necessarily serious. However, up to one in five people will develop serious scarring of the liver, known as cirrhosis. A small percentage develops liver cancer. Advanced liver disease can lead to liver failure and be life-threatening.