Blood Supply and Infectious Disease
Blood Supply and Infectious Disease
In the 1980s, thousands of patients with hemophilia around the world contracted HIV/AIDS through contaminated blood. Many have since died. This tragedy led to new measures to ensure the safety of the blood supply to protect those needing transfusions or blood products. The use of unpaid, voluntary, regular donors is encouraged, and all donated blood units are tested for the presence of transfusion-transmissible infections (TTIs), like HIV and hepatitis, a viral infection of the liver. These changes have meant a dramatic decrease in the risk of contracting a TTI. For the vast majority of people in the United States and Europe, the medical benefits of blood transfusion or blood products now outweigh the risk from infection. However, this is not the case in many developing countries, where lack of resources and infrastructure mean that donors and donated blood may not be screened as carefully.
The major TTIs spread by bloodborne pathogens are HIV, hepatitis B (HBV), and hepatitis C (HCV); in some regions, malaria, syphilis, and Chagas disease might also be transmitted through blood. HIV was first identified in the early 1980s, and a test that could be used for screening blood was discovered in 1985. Before this time, anyone who received blood from an HIV positive donor would have been at risk of getting infected themselves. People with hemophilia, a blood clotting disorder, were especially at risk of HIV, because they depend upon receiving Factor VIII (a protein which helps their blood clot normally) made from pooled blood donations. Over 1,200 people in the United Kingdom developed HIV through contaminated Factor VIII before standardized testing; many have since died of AIDS. According to a 1993 report by the Centers for Disease Control (CDC), more than half the hemophiliacs living in the United States in the early 1980s were similarly infected. A similar situation developed in the general population with HCV, a chronic liver infection that can lead to liver cancer, through exposure before 1990, when little was known of the virus and no test was available. Up to 200,000 Americans may have been infected with HCV through blood transfusion before testing began.
To minimize the risk of TTIs, the World Health Organization (WHO) has developed a two-fold approach to blood safety. First, blood services are encouraged to use only voluntary unpaid donors who have a low risk of carrying a TTI, and use them regularly. Therefore, potential donors answer various health-related questions before blood is taken from them. After this, each unit of donated blood is tested for the most common of the TTIs. In the United States, the Food and Drug Administration (FDA), which controls blood safety, mandates tests for HIV, HBV, HCV, human T-lymphotrophic virus (which can cause leukemia and diseases of the brain and nervous system), and syphilis. In the United Kingdom, the Department of Health requires donated blood to be tested for HIV, HBV, and HCV.
These measures for improving the safety of the blood supply do work. The American Red Cross says that the risk of contracting HIV from blood is now one in 1.5 million units. This risk is 2,000 times lower than it was 1982–1984, when donors and donations could not be screened because there was no test available. Donated blood is generally screened for TTIs using tests that detect either the infectious agent (viruses, in the case of HIV, HBV, or HCV) or antibodies to the infectious agent. Generally, the test results are in the form of a color response, which is read as positive or negative by computer, and the whole procedure is fast enough not to disrupt the supply of blood to those who need it.
HIV took the world by surprise, and there is always the possibility of a new infection that might threaten the blood supply. At present, there is concern over variant Creutzfeld-Jakob disease (vCJD), a rare, fatal brain disease that was first identified in the United Kingdom in 1995. Three cases, out of a total of 158 cases (as of December 2006), have come from contaminated blood. There is currently no test for the prion protein, which is the infective agent in vCJD, so donations cannot be screened. The American Red Cross is dealing with the threat that vCJD could pose to the U.S. blood supply by disqualifying potential donors who have spent periods of time in the U.K. and some other European countries, in case they are infected.
Meanwhile, the safety of blood continues to be a global issue. Many developing countries have not yet adopted the WHO rules. Family or paid donors, known to carry a higher risk of TTIs, account for more than 50% of blood donated in developing countries. The populations in these countries are also at risk from the use of untested blood in transfusions. WHO has a number of projects underway aimed at building and supporting the blood supply around the world, so that everyone has access to safe transfusions and blood products.
WORDS TO KNOW
BLOODBORNE PATHOGENS: Disease-causing agents carried or transported in the blood. Bloodborne infections are those in which the infectious agent is transmitted from one person to another via contaminated blood.
CREUTZFELDT-JAKOB DISEASE (CJD): Creutzfeldt-Jakob disease (CJD) is a transmissible, rapidly progressing, fatal neurodegenerative disorder related to bovine spongiform encephalopathy (BSE), commonly called mad cow disease.
TRANSFUSION-TRANSMISSIBLE INFECTIONS: Any infection that can be transmitted to a person by a blood transfusion (addition of stored whole blood or blood fractions to a person's own blood) is a transfusion-transmissible infection. Some diseases that can be transmitted in this way are AIDS, hepatitis B, hepatitis C, syphilis, malaria, and Chagas disease.
IN CONTEXT: PERSONAL AND SOCIAL RESPONSBILITY
Blood donation is the process in which a person (called a blood donor) voluntarily gives (or donates) blood that will be securely stored at a designated place (often times called a blood bank) for some future use, often times for a blood transfusion. People sometimes donate blood for themselves, particularly when they know that they are scheduled for surgery at a near future point in time.
Transfusion is the medical process of transferring whole blood or blood components from one person (donor) to another (recipient) in order to restore lost blood, to improve clotting time, and to improve the ability of the blood to deliver oxygen to the body's tissues. Whole blood is used exactly as it was received from the donor. Blood components are parts of whole blood, such as red blood cells (RBCs), plasma, platelets, clotting factors, immunoglobulins, and white blood cells. Use of blood components is a more efficient way to use the blood supply, because blood that has been processed (fractionated) into components can be used to treat more than one person. On average, one pint of blood components is used for three patients. Transfusions have saved countless numbers of people around the world. Each year in the United States, about 4.5 million people are in need of blood transfusions.
American Red Cross. “Blood Donation Eligibility Guidelines.” March 21, 2005. <http://www.redcross.org/services/biomed/0,1082,0_557_,00.html> (accessed January 16, 2007). World Health Organization. “Blood Transfusion
Safety.” <http://www.who.int/bloodsafety/en/> (accessed January 16, 2007).