The human immunodeficiency virus (HIV) is a retrovirus that causes AIDS (acquired immune deficiency syndrome). The retrovirus primarily attacks the immune defense system, making the body extremely vulnerable to opportunistic infections. The first reported case of HIV occurred in 1981.
HIV is transmitted from person to person via bodily fluids, including blood, semen, vaginal discharge and breast milk. It can be spread by sexual contact with an infected person, by sharing needles/syringes with someone who is infected, or, less commonly (and rare in countries where blood is screened for HIV antibodies), through transfusions with infected blood. HIV has been found in saliva and tears in very low quantities in some AIDS patients. However, contact with saliva, tears or sweat has never been shown to result in HIV transmission.
The most common type of HIV is known as HIV-1. It is easily transmitted, and it is the cause of most HIV/AIDS infections around the world. HIV-1 has a several subtypes (A through H and O), which have different geographic distributions but produce AIDS similarly. The second type, known as HIV-2, is much less common and less virulent. This form is predominantly found in Africa.
Currently, there is no cure for HIV/AIDS. Patients receive antiretroviral drugs, which suppress the virus. However, these drugs do not reduce the risk of transmitting the disease to someone else.
Researchers estimate that individuals who receive blood transfusions that are contaminated with HIV have a 90% chance of becoming infected.
Since 1985, all blood products in the United States have been screened for HIV-1 antibodies, and since 1992, all blood products have been screened for HIV-2 antibodies. Nucleic amplification tests are used to screen blood and blood products (like plasma, immune globulin and albumin) for infectious diseases in the United States and most other developed countries.
However, blood and blood products in many other countries, especially developing countries, are not regulated as stringently. In fact, the World Health Organization (WHO) estimates that 5-10% of all HIV infections worldwide have been acquired through transfusions of infected blood and blood products. Each year, up to 13 million units out of more than 75 million units of the global blood supply are not screened for HIV or other transfusion-transmissible infections like hepatitis.
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the united states blood supply
Each year Americans donate about 12 million units of blood, which are then processed into 20 million blood products (like plasma, immune globulin and albumin). Each year about 3.6 million Americans receive blood transfusions. The U.S. Food and Drug Administration (FDA) regulates the blood industry, which is responsible for ensuring that the blood products are safe and disease-free. All donated blood must be screened for blood borne pathogens, including HIV, before it can be administered to a patient.
According to the World Health Organization (WHO), the U.S. blood supply is among the safest in the world. Nearly all of the HIV-infections that were acquired through blood transfusions occurred prior to 1985, before donated blood was tested for the virus.
Since March of 1985, all blood products have been tested for antibodies to HIV-1 (the most common type of HIV). Since June 1992, all blood products have also been tested for antibodies for HIV-2 (less common type of HIV that is predominantly found in Africa). Blood and blood products that contain HIV antibodies are safely discarded and not used for transfusions.
According to the FDA, about one in 450,000 to 660,000 blood donations each year contain HIV antibodies, which cannot be detected with current antibody screening tests. This is because the tests detect antibodies to the virus, which may take several months for the body to develop after the virus has entered the blood. In 1996, the FDA recommended that all donated blood and blood products also be screen for the HIV virus itself (HIV-1 p24 antigen). The virus can be detected about one week before the antibodies can be detected.
Currently, the risk of contracting HIV after a blood transfusion in the United States is extremely low. In 1995, the risk of acquiring HIV-1 infection through a blood transfusion was estimated to be between 1 in 450,000 and 1 in 660,000 units of blood. By 2003, this estimated risk decreased to between 1 in 1.4 million and 1 in 1.8 million units of blood.
In general, countries with higher per capita incomes also have high blood donation rates, more available blood, more voluntary donors and more efficient blood collection systems, according to the World Health Organization (WHO).
People who live in developing countries, especially sub-Saharan Africa, are more likely to receive blood that is contaminated with infectious diseases like HIV, hepatitis, malaria and syphilis, than industrialized nations. This is because these countries have a higher prevalence of infectious diseases, inadequate antibody screening (in some countries) and a higher risk of HIV contamination in blood supplies despite antibody screening.
Some countries are unable to test blood because they cannot afford the necessary reagents and test kits. In Sub-Saharan Africa, 22% of countries report that they do not have an adequate system to store blood. They lack the necessary facilities, as well as consistent electricity to refrigerate blood and blood products. (Refrigeration is necessary to prevent bacteria growth in the blood products.) In addition, about 51% of countries in the area report that they experienced interruptions in general blood supplies. This is especially common in areas that are faced with political instability and armed conflict. In addition, poor countries lack funding to employ and train healthcare workers to handle blood and blood products safely.
Many countries are dependent on emergency blood donations from paid donors or family members. In fact, volunteer donors account for less than half of the blood supply in developing countries. However, research shows that blood collected from paid or family donors is more likely to be contaminated with HIV. This is because many HIV-infected individuals have incentive to donate blood if they will receive money. HIV-infected family members may be unaware of their infection, but feel obligated to donate blood in order to help their relative.
In addition, many countries have cultural beliefs that do not support blood donations, and their governments and other federal institutions do little to counteract these ideas. Very few developing countries have made substantial efforts to encourage voluntary blood donation. In areas that have high HIV prevalence rates it may be difficult to identify low-risk volunteer blood donors.
In poor countries, women and children (ages one to three years old) require the most blood transfusions. According to the WHO, more than half a million women die each year from complications related to pregnancy and childbirth worldwide. About 99% of these fatalities occur in developing countries. It is estimated that children who suffer from severe anemia as a result of malaria receive up to 70% of all blood transfusions in Africa.
In countries with a high prevalence of HIV among blood donors, this risk is especially high. However, several studies suggest that blood transfusions are not the major cause of HIV transmission in most countries. Instead, unprotected sexual contact and injection drug use are the main causes of HIV transmission in most countries.
Of the 191 WHO member states, only 43% test blood for HIV, hepatitis C and hepatitis B viruses. Researchers estimate that transfusion-transmitted HIV infection accounts for 80,000 to 160,000 infections annually, contributing 2-4% of all cases of HIV transmission. The WHO estimated that 25% of the blood transfused in Africa was not tested for HIV in 2000. Consequently, about 5-10% of HIV infections in Africa in 2000 were transmitted by blood transfusions.
Since the 1980s, there has been a major international effort to reduce the risks associated with blood transfusion in Africa. In Kenya, the WHO estimates that no more than 2% of blood transfusions contain HIV antibodies. In South Africa, which has a high incidence rate of HIV, the National Blood Service did not find any evidence of HIV transmission through blood transfusions among the 881,673 transfusions provided in 2000.