Successful screening of blood donations for West Nile ongoing

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Aug 14, 2003 (CIDRAP News) – As of June 14, all blood donations in the United States are screened for West Nile virus (WNV) through a program among US blood collection agencies (BCAs) that uses nucleic acid–amplification tests (NATs). The program and its success thus far are described in a report in the Aug 15 issue of Morbidity Mortality Weekly Report, released today. Identification of viremic donations affords the opportunity to quarantine and retrieve all potentially infectious components from the blood supply, says the report.

The screening program comes in response to the fact that 23 persons acquired WNV infection through blood transfusions during the 2002 epidemic. Commercial assays were developed over the 9 months beginning in September 2002. The Food and Drug Administration (FDA) recommends that BCAs, in addition to screening, question donors about fever with headache occurring in the week before donation and defer those who report such symptoms.

Of some 1 million blood donations screened from late June through early August of this year (representing about 95% of the total donations collected in the United States over that period), 329 have been found to be reactive for West Nile infection, with 163 of those reactive on repeated testing. State health departments in Colorado, Florida, Louisiana, Mississippi, New Mexico, South Dakota, and Texas have reported 38 presumptive WNV-viremic donors to ArboNET, the cooperative surveillance project of CDC and state and local health departments. (The remaining reactive donations had not yet been reported to state health departments at the time of the report.)

Screening is done using one of two commercial assays being distributed under phase III investigational new drug approval by FDA that are capable of identifying highly conserved regions of the WNV genome. Aliquots from a group of blood donations are pooled and tested by NAT. If the pool is NAT-reactive, then the individual samples in the pool are tested separately. When an individual NAT-reactive sample is found, that donation is quarantined and all components from the same donor within the previous 14 to 28 days are retrieved. A series of further NATs are then performed on alternate samples from the donation, and testing at a different laboratory is usually done in addition. The original donation and subsequent blood samples from the donor are assayed for WNV-specific IgM antibody as well to determine whether seroconversion has occurred. The donor is questioned within 14 days of donation about travel, exposure, and WNV-like symptoms before and after donation.

An Editorial Note following the report comments on the success of the program. It points out that the screening of all blood donations for HIV and hepatitis C virus put in place in 1999 uses similar methods and formats, providing infrasturcture for and familiarity with the WNV procedure. Also noted is the fact that since the sensitivity of testing in field settings is still under investigation, patients who experience a febrile illness within 4 weeks of receiving a blood transfusion should be reported to CDC through public health authorities to allow initiation of an investigation.

CDC. Detection of West Nile virus in blood donations—United States, 2003. MMWR 2003;52(32):769-72 [Full text]

See also:

American Association of Blood Banks guidance on reporting WNV-viremic blood donors
http://www.blackwell-synergy.com/doi/abs/10.1046/j.1537-2995.2003.00496.x   

FDA guidance for industry on donor suitability and blood safety in known or suspected WNV
http://www.fda.gov/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/Blood/ucm074111.htm

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