Halting West Nile By Transfusion
Medical Editor: Barbara K. Hecht, Ph.D.
Sept. 18, 2003 -- A report on the transmission of the West Nile virus through blood transfusion during the 2002 epidemic was released online today by The New England Journal of Medicine. The study shows that transfused red cells, platelets, and fresh-frozen plasma can transmit the virus and proposes that screening potential donors with the use of RNA-based tests for the virus may reduce or even eliminate this risk.
In the study, there were 23 people who acquired the West Nile virus through transfusions. Ten of the 23 (43%) were immunocompromised because of a transplant or cancer. The immunodeficient recipients who acquired West Nile tended to have unusually long incubation periods before they became ill. Eight of the 23 (35%) people who acquired West Nile virus by transfusion were 70 or over.
Sixteen donors with evidence of viremia (virus in the blood) at the time of donation were discovered to be linked to the 23 infected recipients. Fever, new rash, and painful eyes were associated with being a donor with West Nile viremia. All 16 of these infected donors had been negative for West Nile virus using an antibody test.
In an accompanying editorial, Roger Dodd of the American Red Cross notes that screening of blood donations for West Nile virus using an RNA test was initiated nationwide in late June 2003. By the first week of August 2003 about 1.1 million units had been tested for the viral RNA and 163 found to be positive for the virus. This would appear to validate the effort and expense of testing blood donations for the West Nile virus using the RNA-based test.
The report and editorial were published early in The New England Journal to coincide with a meeting of the Blood Products Advisory Committee of the Food and Drug Administration.
More About Blood Donors Carrying the West Nile Virus
Sept. 19, 2003 -- The new test for West Nile virus has detected the virus in "more than 600 blood donors" across the country this summer, preventing transfusions of the contaminated blood, according to Lawrence K. Altman, MD writing in The New York Times today.
The new test detects the "genetic signature" of the virus -- the RNA that makes up its genome. "Blood banks asked donors about symptoms of recent illnesses, " notes Altman. "But the West Nile virus can be present in blood before symptoms develop or even among people who report few, if any, symptoms."
There was also a major problem with the old antibody-based test for West Nile virus. The problem is that the virus can be present in blood before the person who is infected produces antibodies in response to the virus. So the old test could come up falsely negative and not reflect the fact that the virus was already in the bloodstream.
The new RNA-based test was developed by collaboration between the FDA, blood banks and the biotechnology industry. However, manufacturers have not yet been able to meet the demand so that every blood banks could use it to test every unit of donor blood. Blood banks have therefore generally had to pool blood samples from a number of donors and test the pooled sample. If the test is positive, they then test the blood from each donor in the pool.
The only blood banks that are testing each donor's blood are in some areas where West Nile is particularly prevalent this summer, Those states include Kansas, Nebraska, North Dakota, Oklahoma and South Dakota, according to Julie L. Gerberding, director of the CDC in Atlanta.
Comment: It is clear that the West Nile virus has not yet been completely excluded from the nation's blood supply. The new test has done yeoman's duty in detecting the West Nile virus in "more than 600 blood donors" this summer in the US. But every unit of donated blood must be tested before the blood supply can be said to be free of the West Nile virus.
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Last Editorial Review: 9/19/2003