How HIV is transmitted through blood and blood products? In 150 words
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Introduction
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Transmission of HIV and other blood-borne viruses can occur during transfusion of blood components (ie, whole blood, packed red cells, fresh-frozen plasma, cryoprecipitate, and platelets) derived from the blood of an infected individual.(1,2) Depending on the production process used, blood products derived from pooled plasma can also transmit HIV and other viruses, but recombinant clotting factors cannot.(3,4,5) This chapter discusses the history of HIV transmission through blood products; incidence; control measures; and the current estimated safety of U.S. blood components, blood products, tissues used for transplantation, and sperm used for artificial insemination.
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HIV Infection Transmitted During Blood Transfusion
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Single Donor Components Before 1985
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HIV infection resulting from blood transfusion has been documented repeatedly since the first case report in late 1982.(6-8,9) In the United States, almost all cases are due to blood transfused before March 1985, when HIV antibody testing became available to screen donated blood. As of December 2001, an estimated 14,262 persons have been diagnosed with AIDS as a result of transfusing contaminated blood or blood products.(10)
In some resource-rich countries, testing of donated blood for HIV antibodies was not immediately initiated for a variety of reasons. France began HIV antibody testing in June 1985, Canada began testing in November 1985, and Switzerland began testing in May 1986. Germany inconsistently tested plasma products between 1987 and 1993, as did Japan in 1985 and 1986. These delays led to criminal investigations in France, Germany, Switzerland, and Japan, which in some cases led to criminal conviction of those persons found to be responsible.(11) At least 20 countries initiated compensation programs for at least some individuals infected by transfusion of HIV-contaminated blood and blood products.(11,12)
The risk of HIV transfusion through infected blood products exceeds that of any other risk exposure. Ninety percent of recipients transfused with HIV antibody-positive blood are found to be HIV infected at follow-up.(1) No HIV-infected but persistently seronegative transfusion recipients have been identified. The 90% probability of seroconversion is independent of the age or sex of the recipient, the reason for transfusion, and the type of component transfused (excluding washed red blood cells, which transmit HIV at a lower rate).(13)
HIV infectivity of red blood cell components that were not washed before transfusion decreases as storage time increases. HIV-contaminated red blood cells stored for <8 days are 96% infectious, whereas those stored for >3 weeks are 50% infectious.(1) The level of a donor's viremia at the time of donation is also an important determinant of HIV transmission risk, but no other donor characteristics have been found to affect transmission.(14) Of all transfused patients, half die within 6 months after transfusion from the underlying disease that necessitated the transfusion. Currently, cases involving transfusion of HIV-positive blood do not increase the overall 1-year posttransfusion mortality rate of recipients in the United States. In Zaire, however, patients transfused with HIV-positive blood are 31% more likely to be dead 1 year after transfusion than are patients transfused with HIV-negative blood.(15) This difference is unexplained but emphasizes the importance of screening blood for HIV in developing countries.
HIV disease due to transfusion progresses in the recipient at rates comparable to those in individuals infected for similar duration but by other routes.(16,17) One report found that a transfusion recipient may develop AIDS more rapidly if the infected blood component comes from a blood donor who develops AIDS soon after the time of the blood donation.(18) Other analyses, however, do not confirm this finding.(19) It is more likely that host factors, particularly the recipient's age and immune status, and perhaps other as-yet-undefined cofactors influence the progression to AIDS.(20,21) The mean time of progression to AIDS is estimated to be 8.2 years for adult transfusion recipients who receive no antiretroviral therapy, with a cumulative prevalence of 20% having AIDS 5 years after infection.(22) This progression rate may be overestimated, and the mean time to AIDS development underestimated, because these values are based primarily on data from recipients identified because they developed AIDS or because they received blood from donors who subsequently developed AIDS. The data exclude many donors and recipients who have not been identified because they remain asymptomatic.