In the 1970s, the haemophilia community was devastated by the tragic news that clotting factor concentrates manufactured from human blood, that were used for the treatment of haemophilia, were responsible for widespread transmission of the hepatitis B and C viruses. This was followed by around 60–70% of people with severe haemophilia in Western Europe and the USA becoming infected with the human immunodeficiency virus (HIV) in the early 1980s.
Today, clotting factor concentrates manufactured from donated blood are subjected to rigorous viral inactivation steps during their production, which greatly reduces the risk of viral contamination. This involves heating, filtering and using solvents and detergents to remove or inactivate any potential impurities. While there is still some small risk of infection from a virus called the parvovirus (which can cause anaemia) and from infectious agents known as prions (which can cause Creutzfeldt-Jakob Disease i.e. the human form of mad cow disease), in general, clotting factor concentrates are now associated with a good safety record.
Technological advances have also led to the availability of clotting factor concentrates that are produced by genetic engineering, as opposed to from human blood. Known as recombinant clotting factors, these are free from viral contaminants, and are now used to treat the majority of people with haemophilia.