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z <br />Infection can occur through parenteral exposure <br />(including transfusion of blood or blood products), by the <br />transplacental route as well as through heterosexual <br />intercourse. No cases of casual spread have been <br />identified. It has been confirmed that the risk of <br />nosocomial transmission is very low. <br />Most exposures to HIV in health care workers, either <br />directly by needlestick injuries or indirectly through <br />mucous membrane exposure, do not result in infection of the <br />worker. The CDC followed over 938 cases of health care <br />personnel with such documented exposures. Follow-up periods <br />averaged 15 months. 85% of these exposures were to blood or <br />serum, and 76% involved needlestick injuries or cuts with <br />sharp implements. None of the 938 incidents resulted in the <br />acquisition of signs or symptoms of the acquired immune <br />deficiency syndrome. The CDC stated that the risk of <br />hepatitis B virus infection to health care workers is far <br />greater than the risk of HIV transmission. Following a <br />needlestick injury, the risk of acquiring HBV varies from 6 <br />- 30%. A similar injury results in a risk of HIV infection <br />of less than 1%. <br />Careful observance of the recommendations for pre- <br />vention of transmission of bloodborne pathogens is the most <br />effective means available to reduce the risk of HIV exposure <br />in the blood bank. <br />Miscellaneous Viruses <br />Theoretically, almost any viral agent can be transmitted by <br />blood. These viruses include the Delta agent (a defective <br />virus that requires HBV to replicate), yellow fever virus, <br />Marburg virus and other exotic tropical viruses. In <br />reality, such infections are extraordinarily rare. <br />More anxiety has been expressed regarding the <br />possibility of slow virus transmission by blood trans- <br />fusion. Slow viruses include the agent that causes Creutz- <br />feldt-Jakob disease. Documentation of transmission of this <br />agent by biologic materials is present; however, there is no <br />evidence that the disease has ever been transmitted by blood <br />transfusion. <br />One cannot feel entirely complacent about this <br />potential danger. Because these slow viruses remain latent <br />for many years, it would take a long prospective study to <br />truly evaluate the risk of transmission. There is a single <br />study of 237 infants who received fetal or neonatal blood <br />transfusions and were evaluated 3 - 7 years later. None of <br />these children developed an illness that could be linked to <br />a slow virus. <br />BIOSAFETY - INFAGT - 0491 - PAGE 5 <br />