Harvey Alter, at the US National Institutes of Health, demonstrates during the 1970s that most cases of hepatitis transmitted by blood transfusion correspond neither to the hepatitis A nor the hepatitis B virus, then the only ones known, but to a completely different infectious agent he provisionally names "non-A, non-B hepatitis", whose exact identity remains unknown for more than a decade despite intense searching. Michael Houghton, at the biotechnology company Chiron, succeeds in 1989, using novel molecular cloning techniques from genetic material present in infected blood — with no need to culture the virus in the laboratory, a method that had repeatedly failed — in identifying and sequencing the complete genome of the responsible virus, called the hepatitis C virus. Charles Rice, at Washington University in St. Louis, decisively demonstrates in 1997 that this identified virus is indeed the direct cause of the disease, genetically modifying a laboratory version of the virus and injecting it into chimpanzees, which develop the characteristic hepatitis, thereby fulfilling the rigorous scientific criterion needed to establish viral causality. The discovery makes it possible to develop detection tests that virtually eliminate transmission via blood transfusion in countries that adopt them, and leads, two decades later, to the development of antiviral drugs able to cure chronic infection in more than ninety percent of treated patients.