The 2012 West Nile virus (WNV) transmission season developed into the most severe season since 2003; during this time, AABB published a "Weekly Report News Flash" on Aug. 27, 2012, providing updated information about the 2012 season and suggesting that a "conservative approach for conversion from minipool nucleic acid testing (MP-NAT) to individual donation nucleic acid testing (ID-NAT) and then reversion to MP-NAT — triggering and detriggering criteria — be applied." AABB's Transfusion Transmitted Diseases committee's action was precipitated by the high number of clinical cases, expanse of the outbreak and number of blood centers in outbreak areas going through cycles of triggering and detriggering during the outbreak.
The August 2012 "News Flash" provided additional clarification for blood centers:
"Most blood collection facilities use one to two presumed/potentially viremic blood donations, or PVDs, to trigger conversion from MP-NAT to ID-NAT and continue ID-NAT for seven to 14 days or longer depending on reported WNV activity (donor, mosquito, human clinical cases, animal activity) in an area (defined as the blood collection region or a smaller area within the region). These criteria are more stringent than the recommendations included in Association Bulletin #08-03."
"The recommendations in this bulletin [#08-03] will be reevaluated by the AABB Transfusion Transmitted Diseases committee in conjunction with data generated during this WNV season to determine if further recommendations are warranted."
AABB revised recommendations made in the 2008 Association Bulletin to ensure that facilities are prepared to implement appropriate ID-NAT triggering and detriggering criteria during the 2013 WNV transmission season and in the future. These revisions were published in Association Bulletin #13-02 that was released on June 28, 2013.
The following is a summary of the changes that are included in Association Bulletin #13-02:
Suggested triggering criteria in #13-02
It is recommended that establishments consider use of one of the following criteria for initiating the conversion from MP-NAT to ID-NAT:
One PVD with evidence of other WNV activity in a collection region.
Two PVDs in a seven-day rolling period if there is no other WNV activity reported in a collection region.
One PVD if the collection facility decides not to include considerations of other WNV activity in the region in its triggering decision.
Note: Association Bulletin #08-03 lists the recommended criterion for triggering as two PVDs within a seven-day rolling period (without a rate requirement that had been recommended in earlier bulletins).
Suggested detriggering criteria in #13-02
It is recommended that establishments consider use of the following criteria for resuming MP-NAT from ID-NAT:
Detrigger based on a minimum of 14 days without a WNV initially reactive and in the absence of other indicators of WNV activity.
If these conditions are not met, continue ID-NAT in defined collection regions with ongoing WNV activity in humans, mosquitoes or animals.
Assessments as to when to detrigger could be made at seven-day intervals (e.g., 21 days, 28 days after triggering), corresponding with updates to public health surveillance sites, to determine when MP-NAT should be resumed.
Note: The above recommendations do not state that ID-NAT should continue for an additional 14 days after the cessation of local activity in the absence of WNV-reactive donations. The recommendation states that WNV-reactive donations in combination with local conditions should be evaluated; if conditions indicate that WNV is still present after 14 days, facilities could assess when to detrigger at seven-day intervals. Detriggering is recommended when WNV-reactive donations and local activity, given the available information, are no longer present.
The recommendations in #08-03 also used local activity to clarify detriggering actions:
Detrigger based on a minimum of seven days without a PVD.
Continue ID-NAT for more than seven days in areas with ongoing WNV activity in blood donors from facilities that collect in overlapping areas, or with local conditions (including clinical, avian or mosquito WNV activity, where that information is available in a timely fashion), or with prior trigger history, or at the discretion of the medical director. In these circumstances, continuing ID-NAT for 14 days should be considered.
"Other WNV activity" is clarified in #13-02
"Other WNV activity" is defined in Association Bulletin #13-02 as one or more of the following:
PVDs at another blood center in the collection region.
Human WNV cases reported to county /state health departments or the U.S. Centers for Disease Control and Prevention.
Reports of WNV activity in mosquitoes or animals (e.g., equine or avian).
Equine, as well as avian, WNV activity denotes animal activity in addition to mosquitoes. Association Bulletin #13-02 includes appropriate Web addresses for the CDC and county-level U.S. Geological Survey (USGS) sentinel surveillance maps. The latter site notes that sentinels are usually chickens; however, they may be birds and/or horses.
Note: Bulletin #08-03 recommended consideration of local conditions, including clinical, avian or mosquito WNV activity. The communication plan encouraged a review of clinical or epidemiological evidence of ongoing WNV activity; however the bulletin did not provide resources such as links to the CDC and USGS websites that are provided in Association Bulletin #13-02.
A report by R. Francis et al., published in "Transfusion" in December 2012, described the large WNV outbreak in New York City in 2010 and found a strong correlation between clinical WNV cases (as identified by the CDC and USGS websites) and the occurrence of WNV-reactive donations. Additionally, the authors noted the need to extend triggering periods due to donations that were identified only by retrospective testing during gaps between triggering time periods. Francis and colleagues concluded that "the detection of NAT-positive donations with retrospective testing may indicate the need for changes in our trigger criteria."
Francis, R. O., Strauss, D., Williams, J. D., Whaley, S. and Shaz, B. H. West Nile virus infection in blood donors in the New York City area during the 2010 seasonal epidemic. Transfusion, 2012: 52: 2664–2670.
An article by W.M. Chung et al. that was published the July 2013 issue of the Journal of the American Medical Association, as well as an accompanying editorial by S. Ostroff and literature review by L.R. Petersen et al., describe the Texas outbreak of WNV in 2012. The pieces document that WNV outbreaks "revisit similar geographic distributions, and are strongly predicted by the mosquito vector index." In Chung's study, the Culex quinquefasciatus species-specific vector index predicted the onset of symptoms among WNV neuroinvasive disease cases one to two weeks after increasing infection trends in mosquitoes were detected. The study also revealed that WNV cases clustered in neighborhoods with high housing density reflecting higher vector indices and following geospatial patterns of prior years.
Chung W.M., Buseman C.M., Joyner S.N., et al. The 2012 West Nile Encephalitis Epidemic in Dallas, Texas. JAMA. 2013;310(3):297-307.
Ostroff S. West Nile Virus: Too Important to Forget. JAMA. 2013;310(3):267-268.
Petersen L. R., Brault A. C., Nasci R. S. West Nile Virus: Review of the Literature. JAMA. 2013;310(3):308-315.
As an attachment to the Association Bulletin, AABB provided a listing of facilities that have given contact information for reporting their WNV data on the AABB WNV Biovigilance Network. This listing is intended to assist facilities in making necessary arrangements for real-time communications during the WNV season. Effective communication among all facilities in a collection region (regardless of the number of such collectors) will permit efficient and timely application of triggering and detriggering in each geographic area.
All facilities should work together to create a plan for rapidly communicating WNV-reactive donations/PVDs. This has been most effectively accomplished for past WNV seasons by having a representative from each collection or testing facility as part of a multi-site email link. WNV reactivity, PVDs, confirmed positivity and triggering/detriggering activities are communicated to all participating facilities by such links. Responsibility for rapid reporting of WNV-reactive donations/PVDs in a collection region should be clearly defined among all collection and testing facilities to ensure that each WNV-reactive donation/PVD is reported promptly and only once to the AABB reporting site.
Note: Some delays have already occurred for this WNV season, so it is important to emphasize the importance of reporting WNV-reactive donations/PVDs to the AABB WNV Biovigilance Network and the same including triggering/detriggering activities via email communications.
Contact biovigilance@aabb.org for assistance with reporting information on the AABB WNV Biovigilance Network or to update information on the West Nile Virus Web Reporting Lab Contacts List.
The bulletin states, "The donor's residential zip/postal code should be used as the location of the WNV reactive or PVD. Although exposure may occur at any location, it is most likely that exposure occurred while the donor was at his or her residence (dawn or dusk, when mosquito activity is highest)." In the event of extended travel/vacation by the donor during the incubation period, the zip code that more likely represents the location of the exposure should be used.
Organizations
AABB
American Association of Tissue Banks
American Red Cross
American Society of Hematology
America's Blood Centers
Armed Services Blood Program
U.S. Centers for Disease Control and Prevention
Council of State and Territorial Epidemiologists
Plasma Protein Therapeutics Association
Liaisons
Food and Drug Administration, Office of Blood Research and Review
Food and Drug Administration, Office of Cellular, Tissue and Gene Therapies
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301.907.6977
