Blood Transfusions and Organ Donations

by CDC

How were these cases identified?

After unexplained neurological illnesses resulted in two organ recipients from one donor, serum and plasma collected from the donor were retrieved and tested. The samples tested positive for WNV IgM and IgG antibodies, but were negative for WNV RNA by PCR.

How was the organ donor infected?

It is likely that the organ donor was infected by the bite of an infected mosquito, as he was reported to have spent time outdoors and infected mosquitoes were collected from a site near the person's home approximately 10 days before he died.

What is the current protocol for testing donor or organs before a transplant is conducted?

Organ donors are screened to identify infectious risks on the basis of national organ-procurement standards. Screening of all organ donors with WNV NAT is not currently required or routinely performed for several reasons: 1) NAT is only available through an "Investigational New Drug" applications for blood screening at this time; 2) the length of turnaround time to obtain WNV NAT testing, and 3) the unproven test performance in the organ-donation setting. National guidelines for organ-donor screening are continuously reevaluated by the Health Resources and Services Administration in consultation with FDA, CDC, and organ-procurement organizations.

Which agencies regulate transplant and blood issues?

The US Health Resources and Services Administration (HRSA) and Centers for Medicare and Medicaid Services (CMS) have oversight over organ procurement and transplantation, while the Food and Drug Administration (FDA) regulates tissue and blood.

You have stated that the system of testing donated blood for WNV by nucleic acid-amplification test (NAT) has markedly reduced the risk of transfusion transmission. How is the testing of organs before transplantation different?

There are several issues to consider: (a) time, (b) type of test and (c) potential biological differences.

(a) Time is a critical factor in organ donation; one analysis suggested that WNV NAT screening might result in a net loss of years of life among certain types of potential transplant recipients because screening might exclude healthy donors from an already limited donor pool. The time pressure to test and process donated blood is not as extreme.

(b) Additionally, NAT has not yet been proven as an effective test in the organ-donation setting-it is not known at this time that it would prove as useful as it has in identifying blood donations that pose a risk.

(c) It has been learned through limited retrospective studies that transfused viremic donations did not transmit WNV infection if IgM antibody was present, and investigation of all 30 cases of WNV transmitted by blood transfusion documented to date indicated that the donors' viremias can be of low titer and that all resulted from IgM antibody-negative donations. This instance of organ-transplant-associated WNV transmission suggests that transmission through solid organ transplantation can occur from donors with IgM and IgG antibodies and without detectable nucleic acid by PCR in their serum. Experimental evidence in humans and animals suggests that WNV might persist in organs after clearance of viremia (e.g.., when virus is no longer circulating in the bloodstream.) This would present a different scenario, requiring different testing, than the case of NAT testing of donated blood.

Is there testing available that would have been able to identify the risk of WNV infection before the organs were transplanted?

It is currently unknown whether NAT would have detected West Nile virus in this donor.

What will be done to follow up these cases, and to reduce the risk of WNV infection through transplanted organs in the future?

Clinicians should be aware that transplant-associated infectious disease transmission can occur and should be vigilant for unexpected outcomes in transplant recipients, particularly when they occur in clusters.

Cases of suspected WNV infection through organ transplant should be reported promptly to local and state health departments and CDC.

We will continue the evaluation of the blood donor to the organ donor to look for evidence of WNV infection, and the evaluation of the organ donor serum. When done with our investigation, HRSA, CMS, FDA, CDC, state and city authorities and organ procurement organizations will be working together closely to see if evidence in these cases might be used to develop protocols to reduce risks of WNV infection associated with transplanted organs.

About the Author

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The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.