Hepatitis C is an infectious disease primarily affecting the liver, caused by the hepatitis C virus (HCV). The infection is often asymptomatic, but chronic infection can lead to scarring of the liver and ultimately to cirrhosis, which is generally apparent after many years. In some cases, those with cirrhosis will go on to develop liver failure, liver cancer or life-threatening esophageal and gastric varices. The hepatitis C virus is spread by primarily by blood-to-blood contact associated with intravenous drug use in the developed world or poorly sterilized medical equipment and transfusions in the developing world. The virus persists in the liver in about 85% of those infected. This persistent infection can be treated with medication; peginterferon and ribavirin are the current standard therapy. Overall, between 50–80% of people treated are cured. Those who develop cirrhosis or liver cancer may require a liver transplant, and the virus universally recurs after transplantation. An estimated 130–170 million people worldwide are infected with hepatitis C. No vaccine against hepatitis C is currently available. The existence of hepatitis C (originally "non-A non-B hepatitis") was postulated in the 1970s and proven in 1989. It is not known to cause disease in other animals. Signs and symptoms
 Acute infection
Hepatitis C infection causes acute symptoms in 15% of cases. For those that do manifest symptoms, they are in general mild and vague, including a decreased appetite, fatigue, nausea, muscle or joint pains, and weight loss. Most cases of acute infection are not associated with jaundice. The infection resolves spontaneously in 10-50% of cases being more likely in those who are young and females.  Chronic infection
About 80% of those exposed to the viral develop a chronic infection. Most of those during the initial few decades of the infection have little or no symptoms although chronic hepatitis C can be...