Reacting to an emerging safety threat: West Nile virus in North America
Scientific Support Office, American Red Cross Biomedical Services, Gaithersburg, MD 20887, USA. Developments in biologicals
West Nile virus (WNV) entered North America in 1999 and in 2002 was shown to be transfusion transmitted. With competent mosquito and bird vectors throughout the United States and Canada, WNV clinical disease continues at epidemic proportions. Due to these facts, blood donor screening was implemented prior to the 2003 mosquito season and occurs using a variety of strategies. A combination of minipool (MP) nucleic acid amplification testing (NAT) during the " non-season, " coupled with the conversion to the more sensitive individual donation (ID) NAT in epidemic locations during epidemic times, has been successful in detecting approximately 1500 infected blood donors. Assuming that each donation was infectious and manufactured into 1.45 blood components, testing has therefore prevented close to 2200 recipient infections and potential clinical disease. During this same time, transfusion transmission has occurred from seven MP NAT-nonreactive/ID NAT-reactive units (6 in 2003 and 1 in 2004), or a total of 30 transfusion transmitted cases since WNV has been identified in North America. Because WNV occurs in infected blood donors at low concentrations (i.e., lower viral loads than HIV or HCV with the highest viral load of 580,000 copies/mL observed in a blood donor), a trigger strategy that is used in most of the US consisting of two NAT-reactive donations detected by MP NAT and a frequency of 1:1000 or greater has been developed. Since the full implementation of the MP to ID NAT trigger strategy, there have been no documented WNV transfusion transmissions. Because WNV is an acute infection that only occurs seasonally, other strategies have been proposed, such as seasonal testing, which has been implemented successfully in Canada (Quebec), coupled with a screening question used in the " non-season " of whether the donor has been in the US during the past 56 days; if so, WNV NAT is performed. WNV is an example of an emergent agent in which a rapid series of interventions has been successful in controlling transmission through blood transfusion.
Available from: Gadi Borkow
Available from: Douglas Michael Strong
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ABSTRACT: Infectious diseases and malignancies, albeit rarely, have been
transmitted to patients through the transplantation of human tissue
allografts. This article shows the types of infections that are
known to have been transmitted and the various types of tissue
allografts implicated. Infections have been transmitted by fresh
fiozen bone and tendon; by cryopreserved heart valves, veins,
and skin; and by fresh refrigerated cornea, cartilage, skin, and
artery allografts, but not by the most common type of tissue
used: freeze-dried bone allograft.
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ABSTRACT: Some have suggested that "blood is different," and the role for cost-effectiveness is thus circumscribed. In this article, the authors start by reviewing key concepts in health economics and economic analysis methods. Examples are drawn from published blood safety studies. After explaining the underlying reasoning behind cost-effectiveness analysis, the authors point out how economic thinking is evident in some aspects of transfusion medicine. Some cost-effectiveness study results for blood safety are discussed to provide context, followed by consideration of prominent decisions that have been made in transfusion medicine field. In the last section, the authors conjecture as to why in some cases cost-effectiveness analysis appears to have greater impact than in others, noting the terrible price that is paid in mortality and morbidity when cost-effectiveness analysis is ignored. In this context, the implications of opportunity cost are discussed, and it is noted that opportunity cost should not be viewed as benefits forgone by concentrating on one aspect of blood safety and instead should be viewed as our societal willingness to misallocate resources to achieve less health for the same cost.
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