In the 1970s, a decade before AIDS became epidemic, it was discovered that a hepatitis B (HB) pandemic existed. Hepatitis B, often referred to as serum, or transfusion hepatitis, had been thought to be an iatrogenic disease, caused by western medical technology, and of limited spread outside the developed world. Due to the work of the geneticist Baruch Blumberg, an antigen associated with hepatitis B (the so-called Australian antigen) was accidentally discovered, and from that discovery a blood test for the virus developed. With the aid of the test, it was found that hepatitis B was the most widespread viral disease in the world, infecting billions of people, especially in Asia and sub-Sahara Africa. It was also discovered that between 200,000,000 and 300,000,000 people were chronic carriers of the disease and constituted an infectious reservoir for the virus. In some Asian countries, such as Vietnam, fully 15–20% of the population were carriers of the disease.

In addition, researchers discovered that chronic hepatitis B infection was highly associated with the development of liver cancer; hepatitis B being a necessary (though not sufficient) cause of most of the world's liver cancer; and, in turn, liver cancer was the most frequent cancer in developing countries. Chronic carriership was also correlated with cirrhosis of the liver; most cirrhosis being caused by HB infection, not alcohol consumption.