Hematology 2001 433 Reducing the Risk of Blood Transfusion Edward L. Snyder and Roger Y. Dodd There are continuing concerns over the safety of the nation’s and the world’s blood supply. The allogeneic blood supply is tested for antibodies to HIV1/2, HTLVI/II, hepatitis B, hepatitis C (HCV) and syphilis. Testing is also performed for donor ALT (SGOT) levels, for the presence of hepatitis B surface antigen, human immunodeficiency virus (HIV) p24 antigen and, using nucleic acid amplifica- tion testing (NAT), for HIV and HCV nucleic acids. Still, there are concerns regarding other pathogenic agents. Dr. Roger Dodd addresses a series of patho- gens that are already known to be transmissible by transfusion. These include malaria, Chagas’ dis- ease, babesiosis, bacteria and some viral agents. The need for new donor screening assays to protect the integrity and purity of the blood supply must be balanced against the loss of potential donors and the cost of developing and implement- ing these new screening assays. This issue will be highlighted. Dr. Edward Snyder reviews the status of research into development of systems for pathogen inactivation (PI) of blood and its components. A proactive technology wherein PI reagents such as psoralen, riboflavin, dimethylmethylene blue or inactine are added to blood collection bags could assure multiple log reduction of a variety of patho- gens including viruses, bacteria, protozoa and fungi without the need to initially pre-screen the blood for a specific pathogen. Such a program could also cover new pathogens as they enter the blood supply. As a key issue relates to the toxicol- ogy of these agents, Dr. Snyder provides data on a novel carcinogenicity assay that uses a heterozy- gous p53 knock-out mouse model. The criteria likely to be needed for PI technology to be adopted by the transfusion community are summarized. I. EMERGING INFECTIONS AND THE SAFETY OF THE BLOOD SUPPLY Roger Y. Dodd, PhD* There has been great progress in the assurance and main- tenance of the microbiological safety of the blood sup- ply. Indeed, the risk of being infected by a unit of blood has decreased by three to four orders of magnitude over the past thirty years. 1 Particular success has been achieved for hepatitis C and HIV/AIDS, where large- scale implementation of nucleic acid testing has reduced the risk to negligible levels. 2 In contrast, little effort had been directed to a variety of parasitic and arthropod- borne infections. Although most of these are very rarely transmitted by transfusion in the US, their importance is increasing relative to the declining risk of the more fa- miliar transfusion-transmitted infections. In addition, many of these agents qualify as emerging infections. Malaria Malaria is one of the most widespread infections glo- bally and is undoubtedly responsible for the majority of all cases of transfusion-transmitted disease in the world. On a global basis, there may be 300 to 500 million cases of malaria each year, although as few as 10% of all cases are reported. At any one time, as many as 250 million individuals may be circulating infectious parasites. The greatest threat of transmission by transfusion obviously occurs in those regions of greatest endemicity. A number of factors are leading to an increased in- cidence of the disease, particularly in some areas previ- ously thought to be free of infection. More specifically, climate change is leading to an expansion of the geo- graphic range in which the parasite is effectively main- tained and transmitted by the mosquito vectors. Further, the increased speed and range of population movement introduces many more infected individuals into areas in which conditions are suitable for the transmission of in- fection. Finally the geographic range of drug-resistant strains of the parasites is increasing. Currently, malaria is a minor risk of transfusion in the United States, with only about one case for every 3- * American Red Cross, Holland Laboratory, Transmissible Diseases Department, 1560 Crabbs Branch Way, Rockville MD 20855