Organ Transplants:

Current Organ Procurement and Transplantation Network (OPTN) policy requires that living donors be evaluated for risk of transmitting WNV to recipients. Since the majority of WNV infections are asymptomatic, clinical screening will not effectively identify infected donors. Laboratory screening is thus recommended during periods of human WNV activity where the donor lives, works, or travels. Establishing a relationship with local blood banks allow transplant centers to conduct testing only during periods of human WNV activity and reduce false positive results and as well as testing costs.

Seasonal testing during potential periods of WNV activity (May to November) is an alternative strategy but would potentially have a higher false positive rate and be less cost effective. While transmission of WNV from NAT negative (no viremia) but IgM positive donors has occurred, the performance of IgM assays as screening tests has not been validated and cannot be routinely recommended.

No proven cases of donor-derived WNV infection from living donors have been reported. However, 9 deceased donors have transmitted WNV to 18 of 26 (69%) recipients. In at least two cases, the source of the WNV was blood transfusions received by the donor. Disease in recipients typically developed soon after transplantation, and outcomes have been poor with encephalitis or other severe neurological disease commonly occurring. In some cases, transmission has occurred from NAT negative IgM positive donors, suggesting that WNV may be present in organs and transmissible after the virus has cleared from the plasma.

However, screening organs for WNV poses particular problems, so universal screening has not been recommended.  There are nucleic acid tests  (NATs) available for use in screening organ and tissue donors, but a number of factors makes this screening impractical in most cases:

• There are currently two FDA-licensed NAT donor screening assays; these are routinely performed at blood banks or some reference labs but are not commonly available in hospital laboratories.
• The turn-around time from the time the donor blood sample is drawn until the results are reported back may be 24 hours or longer, depending upon availability of testing.  For non-urgent living donor transplants, this turn-around time isn’t a problem, but for deceased donors, the time may exceed the viability limit for an organ or tissue.

• Defer potential donors with encephalitis, meningitis, or flaccid paralysis of undetermined etiology who resided in geographic areas with known WNV activity.
• Exercise a high index of suspicion of WNV infection if an organ transplant recipient develops a febrile illness.  Perform an WNV IgM (antigen) test and a WNV—NAT if WNV infection is clinically suspected.
• Consider screening of living donors with WNV-NAT as close to the time of donation as possible, and then defer donation for 28 days if testing is positive. 

For deceased donors, HRSA recommends transplanting an infected organ only if the potential recipient has an emergent, life-threatening illness and no other organs or life-saving measures are available.

Instant feedback:

References

U.S. Department of Health & Human Services. Organ Procurement and Transplantation Network. Identifying Risk Factors for West Nile Virus (WNV) During Evaluation of Potential Living Donors. Retrieved 11/3/17. https://optn.transplant.hrsa.gov/resources/guidance/identifying-risk-factors-for-west-nile-virus-wnv-during-evaluation-of-potential-living-donors/