1. Home>
2. Specialties>
3. Infectious Diseases>
4. Summary and Comment

West Nile Virus Transmission Through Blood Transfusion

A national blood donation-screening program, prompted by transfusion-associated West Nile virus, diminishes risk for transmission by this route.

In 2002, several case reports implicated blood transfusions, organ transplants, and breast-feeding in the transmission of West Nile virus (WNV; see Journal Watch Infectious Diseases Nov 8 2002), leading to the introduction of a national blood donation-screening program for the virus this past spring. Two reports now detail the cases of transfusion-associated WNV infection and the performance of the ensuing blood donation-screening program.

Pealer and colleagues identified 23 blood-transfusion-associated WNV infections in the U.S. in 2002. Patients were 7-90 years old; 10 were immunocompromised. Fifteen recipients had WNV-associated illness (meningoencephalitis in 13, fever in 2) that began 2-21 days following transfusion. The cases were linked to 16 donors with WNV viremia at donation, and transmission was associated with red blood cells, platelets, and fresh-frozen plasma. Nine of 14 interviewed donors remembered having symptoms suggestive of viral illness (e.g., fever, new rash, painful eyes) before or after donation. For all implicated donors, samples obtained at donation were negative for WNV IgM antibody and virus levels were <80 plaque-forming units/mL.

As detailed by the CDC, between late June and mid-September 2003, approximately 2.5 million blood donations in the U.S. were screened for WNV by nucleic acid-amplification tests. Screening is initially done with minipools of blood donations; upon positive results, individual donations are tested. By mid-September, 601 individual samples had repeatedly tested positive, and 209 additional donations were under further investigation. Among 333 donors for whom information was available, 296 remained asymptomatic after donation, 35 had fever, and 2 had developed meningoencephalitis. One large blood-collection agency retested individual blood samples from donations that had originally passed minipool screening in U.S. regions with a high prevalence of WNV-positive donations and found several WNV-positive samples. Although the donations were immediately quarantined, transfusion-associated WNV infection has been identified in 2 individuals transfused before the new test results were obtained.

Comment: As noted by an editorialist, such rapid implementation of a national blood-screening program is truly remarkable. Unfortunately, these reports demonstrate that WNV transmission can still occur through donations from asymptomatic donors with extremely low-level viremia. To improve blood-supply safety further, donors must be screened postdonation for symptomatic illnesses, and more-sensitive nucleic acid-amplification tests must be developed.

— Richard T. Ellison III, MD

Published in Journal Watch Infectious Diseases October 10, 2003

Citation(s):

Pealer LN et al. Transmission of West Nile virus through blood transfusion in the United States in 2002. N Engl J Med 2003 Sep 25; 349:1236-45.

• Original article (Subscription may be required)
• Medline abstract (Free)

Dodd RY. Emerging infections, transfusion safety, and epidemiology. N Engl J Med 2003 Sep 25; 349:1205-6.

• Original article (Subscription may be required)
• Medline abstract (Free)

Update: Detection of West Nile virus in blood donations -- United States, 2003. MMWR Morb Mortal Wkly Rep 2003 Sep 26; 52:916-9.

• Medline abstract (Free)