NoBlood

Jan B. Wade · #1 (**permalink**) 05-18-2003, 08:14 AM

Risk of West Nile Virus (WNV) Infection by Blood Transfusion

September 27, 2002

The following information is being disseminated by the American Association of Blood Banks (AABB) to assist media outlets with preparation of stories concerning the West Nile virus (WNV) issue relating to blood transfusion. Should members of the media wish to speak with an AABB medical representative, please contact AABB's public relations department by calling (301) 215-6526, or by emailing publicrelations@aabb.org.

The Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the Health Resources and Services Administration (HRSA), and the blood banking community are investigating possible cases of post-transplant or post-transfusion WNV. One investigation in Georgia indicates that WNV transmission can occur via organ transplantation. In another investigation in Mississippi, the isolation of live WNV in a blood product indicates that the virus can survive in some blood components and probably can be transmitted by transfusion. There is also a case under investigation in Michigan in which two patients tested positive for WNV after receiving blood components from the same donor. The donor sample subsequently tested positive for WNV. This case provides additional proof that WNV may be spread through blood transfusion.

Given our current knowledge, the frequency of transmission of WNV through blood transfusion is judged to be extremely low. 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 only a few days. 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.

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. The US Public Health Service (FDA, CDC, and NHLBI) are working with the blood banking community to carry out research studies to better determine the risk of acquiring WNV from a blood transfusion.

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. The blood banking community is working with the FDA, CDC, and test manufacturers to develop a suitable test as rapidly as possible should testing of all blood donations be needed.

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.

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. The FDA is working with blood banks to develop more specific information.

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.

CDC has recently reported that WNV can cause acute flaccid paralysis, a polio-like syndrome that may be confused with Guillain-Barre syndrome. In the event that a recent transfusion recipient develops acute flaccid paralysis, 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.