This year’s (2021) Nobel prize for medicine or physiology has been awarded to Harvey Alter of the U.S. National Institutes of Health (NIH); Michael Houghton of the University of Alberta, Edmonton; and Charles Rice of Rockefeller University, for their discovery of the Hepatitis C virus.

Hepatitis C is a liver disease caused by the hepatitis C virus (HCV): the virus can cause both acute and chronic hepatitis, ranging in severity from a mild illness lasting a few weeks to a serious, lifelong illness. Hepatitis C is a major cause of liver cancer. The World Health Organization (WHO) estimates that 71 million people worldwide are chronically infected with hepatitis C, which causes nearly 400,000 deaths per year, mostly from cirrhosis and liver cancer.

In the 1970s, Alter and his colleagues studied hepatitis in transfusion recipients and showed that even though screens for the hepatitis B virus could reduce the number of cases, many remained. Hepatitis A, a virus transmitted via water or food, wasn’t the explanation either. In 1978, Alter showed that plasma from patients with unexplained hepatitis could cause disease when transferred to chimpanzees, indicating it was caused by an infectious agent. In additional experiments using chimpanzees the only animals susceptible to hepatitis C Alter and his colleagues showed the disease was likely caused by one or more viruses.

Houghton, then working at Chiron Corporation in Emeryville, California, and his colleagues identified the virus on the basis of genetic material from infected chimpanzees, showing that it was a new kind of RNA virus that belonged to the Flaviviridae family. They named it hepatitis C virus. A team led by Rice, then based at Washington University in St. Louis, Missouri, used genetic-engineering techniques to characterize a portion of the hepatitis C genome responsible for viral replication, demonstrating its role in causing liver disease.

The results of research by the Nobel prize for medicine winners and other people has led to significant improvements in hepatitis testing and treatment. In the past decade, harsh and poorly effective treatments for the infection have been replaced by drugs that directly block the virus. These medicines have the potential to cure the vast majority of hepatitis C infections, but their high cost has limited access in many low- and middle-income countries.