Hepatitis C

Hepatitis C is a bloodborne virus that quietly destroys the liver over years or decades. Roughly 50 million people are chronically infected worldwide, and the disease kills hundreds of thousands every year through cirrhosis and liver cancer.

The disease

Hepatitis C spreads through blood-to-blood contact: shared needles among people who inject drugs, unsafe medical procedures, and — before 1992, when routine screening began — blood transfusions. Most newly infected people have no symptoms at all. About seven in ten go on to develop a chronic infection that can sit silent in the liver for years or decades before any problem shows up.

That long, quiet phase is what makes the disease so dangerous. Over time the chronic infection scars the liver. Once enough scarring has built up the liver starts failing (cirrhosis), and the risk of liver cancer rises sharply. By 2014, hepatitis C had become the single greatest cause of infectious death in the United States.

A modern cure — and what's still missing

The treatment picture transformed around 2014, when direct-acting antivirals like sofosbuvir reached the market. The new pills cure more than 95% of chronic infections in 8 to 16 weeks, with manageable side effects. Older interferon-based regimens took six months to a year, made patients miserable, and worked about half the time.

But that cure doesn't reach everyone. Many infected people don't know they're infected. Cost, access, and stigma keep others from being treated. And no vaccine exists yet — HCV mutates rapidly and has seven major genotypes, which has frustrated decades of vaccine research. Reinfection is possible even after a cure.

Folding@home studies some of HCV's proteins to understand how they function, and how to keep treatments working as the virus evolves.