AABB PulsePoints No. 530, September 4, 2002 (REVISED Sept. 5, 2002 - bullets 2, 3 & 7)

(CBBS Web Master Note - Also see more recent communications link at the bottom of this page)

Emerging News Regarding West Nile Virus

The following talking points have been developed by AABB to update members and media regarding emerging news about West Nile virus (WNV).

• The Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the Health Resources and Services Administration (HRSA), the Georgia State Division of Public Health, and the Florida Department of Health are investigating illnesses among four recipients of organ transplants from a single donor. WNV infection was confirmed in the organ donor by detection of viral genomic material by PCR in a serum sample obtained on the day of death. Because of injuries sustained during a motor vehicle accident, the donor had received numerous transfusions of blood products before death. WNV infection has been confirmed in three of the organ recipients; the fourth recipient has not yet been tested. Although the sources of the recipients' infections have not yet been confirmed, this case cluster strongly suggests that WNV can be transmitted by blood transfusion.
• Given our current knowledge, the frequency of transmission of WNV through blood transfusion is judged to be relatively small. The risk of becoming infected with the WNV from a mosquito bite is far greater than becoming infected from a blood transfusion.
• For a transmission to occur, a person would need to make a blood donation while the virus is still in the person's blood. It is unknown for how long the virus persists in blood after a bite from an infected mosquito, but data suggest that it is no longer than several weeks. Approximately 20 percent of infected individuals will become sick with flu-like symptoms within the same length of time, and, hence, would be ineligible to donate blood. Transfusion-transmission could occur from the other 80 percent of infected persons who do not become ill, if they donate during the limited time interval when WNV is in their blood.
• Investigators from the CDC have developed a mathematical model to calculate the risk of WNV transmission by blood transfusion during the peak of a WNV epidemic in Queens, NY, in 1999. Their model included many assumptions. Using this model, it was concluded that the risk of WNV infection by transfusion during the time when clinical cases were detected (approximately one month) was almost two per 10,000 donations. It is not known if this is an accurate estimate. No cases of transfusion-transmitted WNV were detected during this epidemic.
• The risk of infection will be highest in those geographic areas with the most cases and at the peak time of the epidemic.
• The risk of transfusion-transmitted WNV in most of the U.S. at present should be regarded as extremely low, and the risk of developing significant clinical disease as a result of such transmission is even lower. It is likely that the risk of significant clinical disease is greatest in patients who are immunosuppressed.
• Since blood may be collected in one area of the country and used in another location, the risk of WNV transmission, although extremely low, may still exist in areas of the U.S. without any reported cases.
• There is no current test or simple screening question that could be used to detect infectious donors.
• FDA and CDC issued alerts to blood banks and organizations to be vigilant in excluding individuals who may have early symptoms of WNV from donating blood. In addition, FDA and CDC have asked that blood banks and others report any cases where a blood recipient develops WNV for investigation of whether transfusion could have been involved. Such an investigation is now being conducted by CDC to determine whether blood transfusion or donor organs may have been a source for the possible WNV cases in the current transplant recipients.
• In the context of the current WNV outbreak, blood banks should carefully review their policies for managing post donation information from donors who experience fever and headache.
• Although there are no data about stability of WNV in refrigerated blood or blood components, flaviviruses in general are known to survive over long periods in fluids with high protein content; hence would be expected to have good stability in blood.
• If WNV is transmitted by blood transfusion, it is unknown if the symptoms in the recipient would be none, minor (a flu-like illness) or severe (e.g. neurological disease). In the event that a recent transfusion recipient develops meningitis or encephalitis, WNV should be considered in the differential diagnosis.
• WNV is a lipid-enveloped virus and therefore is expected to be destroyed during the viral inactivation procedures used in the plasma derivative manufacturing process. Therefore, there should be no risk of transmission to recipients of manufactured plasma products. This information can be located on AABB's Web site by visiting www.aabb.org and clicking on the "Pressroom" or by visiting the "Member's Area/Latest News."

For additional information about WNV, visit:

http://ww.fda.gov/cber/safety/westnile.htm,
http://www.cdc.gov/od/oc/media/pressrel/r020903.htm, or http://www.cdc.gov/ncidod/dvbid/westnile/index.htm.