Stramer S L
Scientific Support Office, American Red Cross Biomedical Services, Gaithersburg, MD 20887, USA.
Dev Biol (Basel). 2007;127:43-58.
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.
西尼罗河病毒（WNV）于1999年进入北美，2002年被证实可通过输血传播。由于美国和加拿大各地都有适宜的蚊虫和鸟类传播媒介，WNV临床疾病仍呈流行态势。基于这些情况，在2003年蚊虫季节之前就实施了献血者筛查，且采用了多种策略。在“非流行季节”采用混合样本（MP）核酸扩增检测（NAT），并在流行期间对流行地区改用更灵敏的单份献血（ID）NAT，这种组合已成功检测出约1500名受感染的献血者。假设每份献血都具有传染性且制成1.45个血液成分，那么检测因此预防了近2200例受血者感染及潜在的临床疾病。在此期间，有7个MP NAT阴性/ID NAT阳性单位发生了输血传播（2003年6例，2004年1例），自WNV在北美被发现以来，输血传播病例总数达30例。由于WNV在受感染献血者中的浓度较低（即病毒载量低于HIV或HCV，在一名献血者中观察到的最高病毒载量为580,000拷贝/毫升），美国大部分地区采用了一种触发策略，即由MP NAT检测出两份NAT阳性献血，且频率为1:1000或更高。自全面实施MP到ID NAT触发策略以来，尚无WNV输血传播的记录。由于WNV是一种仅季节性发生的急性感染，还提出了其他策略，如季节性检测，该策略已在加拿大（魁北克）成功实施，同时在“非流行季节”使用一个筛查问题，即询问献血者过去56天内是否去过美国；如果去过，则进行WNV NAT检测。WNV是一个新兴病原体的例子，一系列快速干预措施已成功控制了通过输血的传播。
