Hemophilia therapy and blood-borne pathogen risk.

For a brief period, modern medical science was considered to have relegated infectious disease to that of a minor clinical challenge. However, several infectious diseases have emerged or re-emerged in recent years, raising epidemiological concerns, as well as issues over the availability of effective measures of control and treatment. Invariably, these infectious agents have been studied carefully in relation to the safety of blood products, often resulting in concern and action. Emerging diseases arise from many sources. Some are the result of viruses crossing the species barrier from animals to humans. In addition, combinations of these newly identified viruses may make each more difficult to treat, as in the case of human immunodeficiency virus and hepatitis C virus coinfection. Still others can arise from completely new biological mechanisms, such as the prion disease variant Creutzfeldt-Jacob disease, which has spread from infected cattle to humans, particularly in the United Kingdom. The emergence of new viruses and new disease sources has had a significant impact on coagulation factor therapies and blood donation policies. We must deal with these multiple threats and their potential to compromise the safety of our blood supply.