Viral hepatitis is a very common infectious disease responsible for causing more than 1.5 million annual deaths among afflicted patients. Despite the fact that extensive data reports on viral hepatitis have been first established at the beginning of the 20th century, the causes of the disease remained unknown until the 1940s, when the implication of a new virus in triggering the disease was first revealed. Performing additional research on hepatitis, virologists have later discovered two major distinctive types of hepatitis: hepatitis type A and hepatitis type B. Concerned by the increasing numbers of hepatitis cases due to blood transfusions, medical scientists have conducted a series of more elaborate medical investigations in order to identify conclusive facts regarding the occurrence and progression of hepatitis.

Intrigued by the fact that increasingly larger numbers of persons who received blood transfusions experienced symptoms such as high fever, chills and skin rashes, doctors decided to carefully analyze a series of immune reactions to foreign proteins in blood samples taken from such persons in order to reveal the exact sources of their symptoms. After comparing the immune reactions of the persons who had been administered blood transfusions with those of people in good health, medical scientists were able to reveal a type of protein that rarely reacted with antibodies produced by the immune system.

Due to the fact that the analyzed immune reaction was extremely rare, medical scientists concluded that it wasn't caused by genetic particularities in the human blood, but by a certain type of infectious agent. The discovered infectious agent later received the name of antigen Aa. After continuing their research on blood proteins, doctors discovered a correlation between antigen Aa and hepatitis. Researchers later concluded that antigen Aa was actually a component part of the virus identified to cause hepatitis B.

The findings determined medical scientists to take additional measures in preventing the occurrence of hepatitis among the population. By testing blood transfusions for the presence of the causative virus, scientists hoped to reduce the risks of transmitting hepatitis from one individual to another. The method used to detect the presence of the virus in the blood was given the name of radioimmunoassay. In present, this technique is still used to test the integrity and safety of blood transfusions and other blood products. Appreciated for its efficiency and reliability, radioimmunoassay is the predecessor of today's modern techniques used in blood screening.

Another breakthrough consisted in finding an effective vaccine against hepatitis. For the first time in history, the main curative agent used in creating the vaccine was actually a modified strain of the causative virus. By altering the virus in the laboratory and introducing it in a vaccine, virologists were able to stimulate an immune reaction to that particular virus in the human body. A few years later, the ongoing research conducted on hepatitis led to another crucial discovery: the HCV ? hepatitis C virus. Short after, medical scientists came up with efficient vaccines for all existing hepatitis virus types: A, B and C.

Over a period of only a few decades, doctors discovered valuable facts on hepatitis, as well as efficient methods of preventing its transmission. Thanks to the remarkable findings of several pioneer virologists and biologists, medical science was revolutionized and the mystery around many different viral infectious diseases was finally unveiled.