(Inside Science) -- The 2020 Nobel Prize in physiology or medicine has been awarded to three scientists "for the discovery of Hepatitis C virus."

The prize goes jointly to Harvey J. Alter of the National Institutes of Health, Michael Houghton of the University of Alberta, and Charles M. Rice of the Rockefeller University in New York.

Hepatitis B and C are bloodborne diseases that can cause cirrhosis and cancer of the liver, leading to death or the need for liver transplants. Both are caused by viruses that can hide in the body for months or years without causing symptoms, which made them difficult to discover. In the mid-20th century, a large fraction of patients who received blood transfusions later developed hepatitis.

Baruch S. Blumberg discovered the hepatitis B virus in 1967, and soon afterward developed tests to screen blood samples for the virus and a vaccine to prevent infection. He won the Nobel Prize in physiology or medicine for his work in 1976. But it soon became clear that only some of the hepatitis infections from blood transfusions were caused by the hepatitis B virus.

Alter and his colleagues focused on the remaining cases of transfusion-related hepatitis. In the 1970s, they showed that blood from hepatitis patients could transmit the mysterious disease to chimpanzees, proving that the illness was caused by an infectious agent. The researchers later determined that this agent was an unknown virus.

In the late 1980s, Michael Houghton discovered the virus itself while working at the pharmaceutical firm Chiron. He used antibodies from hepatitis C patients as detection tools to identify sequences of the virus's DNA, which he cloned from DNA fragments in the blood of an infected chimpanzee. Charles M. Rice at Washington University in St. Louis and his colleagues then used genetic engineering to demonstrate that the virus Houghton discovered could, on its own, cause the disease hepatitis C.

"This was the first time these types of molecular-based approaches were used to identify a novel virus," said Gunilla Karlsson-Hedestam, an immunologist and member of the Nobel committee, during a press conference.

The discoveries of this year's winners led to tests that cleaned the blood supply, preventing nearly all cases of hepatitis from transfusions. It also led to the development of antiviral drugs that can cure the disease in the vast majority of patients. 

"These developments have saved millions of lives worldwide," said Karlsson-Hedestam. "Continued efforts to implement blood screening and treatments globally raise hope that hepatitis C virus can be controlled and eventually eliminated."

For more of Inside Science's coverage of the 2020 Nobel Prizes in Physiology or Medicine, Physics, and Chemistry, please visit our Nobel coverage page. For our predictions of the Nobel Prizes in Physics and Chemistry (and to review our Physiology or Medicine picks), please read our predictions story.