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What is West Nile Virus and is there a risk of transmission through blood transfusion?

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asked Jun 8, 2012 in Glossary by Hatice Simsek MD (3,070 points)
edited Jun 8, 2012 by LarryEitel

5 Answers

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What Is West Nile Virus?

West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall. This fact sheet contains important information that can help you recognize and prevent West Nile virus.


What Are the Symptoms of WNV?

  • Serious Symptoms in a Few People. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
  • Milder Symptoms in Some People. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks.
  • No Symptoms in Most People. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all.


How Does West Nile Virus Spread?

  • Infected Mosquitoes. Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.
  • Transfusions, Transplants, and Mother-to-Child. In a very small number of cases, WNV also has been spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby.
  • Not through touching. WNV is not spread through casual contact such as touching or kissing a person with the virus.

answered Jun 11, 2012 by Hatice Simsek MD (3,070 points)
0 like 0 dislike N Engl J Med. 2003 Sep 25;349(13):1236-45. Epub 2003 Sep 18. Transmission of West Nile virus through blood transfusion in the United States in 2002. Pealer LN, Marfin AA, Petersen LR, Lanciotti RS, Page PL, Stramer SL, Stobierski MG, Signs K, Newman B, Kapoor H, Goodman JL, Chamberland ME; West Nile Virus Transmission Investigation Team. Source Epidemic Intelligence Service, Division of Applied Public Health Training, Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. Abstract BACKGROUND: During the 2002 West Nile virus epidemic in the United States, patients were identified whose West Nile virus illness was temporally associated with the receipt of transfused blood and blood components. METHODS: Patients with laboratory evidence of recent West Nile virus infection within four weeks after receipt of a blood component from a donor with viremia were considered to have a confirmed transfusion-related infection. We interviewed the donors of these components, asking them whether they had had symptoms compatible with the presence of a viral illness before or after their donation; blood specimens retained from the time of donation and collected at follow-up were tested for West Nile virus. RESULTS: Twenty-three patients were confirmed to have acquired West Nile virus through transfused leukoreduced and nonleukoreduced red cells, platelets, or fresh-frozen plasma. Of the 23 recipients, 10 (43 percent) were immunocompromised owing to transplantation or cancer and 8 (35 percent) were at least 70 years of age. Immunocompromised recipients tended to have longer incubation periods than nonimmunocompromised recipients and infected persons in mosquito-borne community outbreaks. Sixteen donors with evidence of viremia at donation were linked to the 23 infected recipients; of these donors, 9 reported viral symptoms before or after donation, 5 were asymptomatic, and 2 were lost to follow-up. Fever, new rash, and painful eyes were independently associated with being an implicated donor with viremia rather than a donor without viremia. All 16 donors were negative for West Nile virus-specific IgM antibody at donation. CONCLUSIONS: Transfused red cells, platelets, and fresh-frozen plasma can transmit West Nile virus. Screening of potential donors with the use of nucleic acid-based assays for West Nile virus may reduce this risk.
answered Jun 11, 2012 by Hatice Simsek MD (3,070 points)
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Transfusion. 2005 Apr;45(4):487-91.

West Nile virus in Canadian blood donors.

Cameron CReeves JAntonishyn NTilley PAlport TEurich BTowns DLane DSaldanha J.


Canadian Blood Services, Ottawa, Ontario, Canada.



Blood donation screening for West Nile virus (WNV) RNA by nucleic acid testing (NAT) was implemented in Canada in July 2003, and 14 WNV RNA-positive donations were identified. Samples were screened in minipools of six donations with a WNV assay (TaqScreen, Roche). Two of the donors were identified by single-donor screening that was initiated in the province of Saskatchewan, which had the highest prevalence of WNV in the country, in early September 2003.


The original 14 samples and follow-up samples (2-35 days after donation), available from 13 of the 14 donors were tested with an in-house, real-time, quantitative WNV NAT assay that was specific for WNV. A Health Canada reference reagent was used for calibration. Immunoglobulin M (IgM) and immunoglobulin G (IgG) levels were determined with commercial enzyme-linked immunosorbent assay kits.


All donors tested positive for the presence of WNV with the in-house assay. Two donors, 18 and 19, identified by single-donor testing, had extremely low levels of viremia and that could only be detected in 1:38 or 1:39 replicate tests. The titers of the remaining index samples ranged from below log2.8 (the limit of quantitation) to log4.7 NAT detectable units per mL. Three samples, from Donors 17, 18, and 19, were IgM-positive, whereas samples from Donors 18 and 19 were also IgG-positive. The remaining 10 donors with follow-up samples all seroconverted.


The 14 WNV donor samples detected by routine screening were confirmed as WNV RNA-positive by a WNV RNA-specific in-house assay and by demonstration of seroconversion in 13 of the 14 donors.

answered Jun 11, 2012 by Hatice Simsek MD (3,070 points)
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West Nile Outbreak on Track to Be Worst Ever

47 Deaths; Texas Especially Hard Hit
Aug. 22, 2012
West Nile virus can be transmitted by blood transfusion. In the U.S., blood is tested for West Nile virus. So far this year, West Nile virus has been detected in 242 samples of donated blood. There have been no known infections via transfusion, and the U.S. blood supply is considered safe.
answered Aug 23, 2012 by Hatice Simsek MD (3,070 points)
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My opinion based on thorough reading of published medical literature is, yes. Transfusion of blood products can transmit the West Nile virus.

“Both these patients received cryoprecipitate, a product pooled from many patients. Though the safety of such products has improved markedly with viral detection and inactivation methods, review of the literature reveals that there is, and will likely continue to be, some element of hazard. What if a Witness patient received a blood-borne pathogen or had another severe effect (West Nile, Creutzfeldt-Jakob disease, etc.) from our conscientious care? If we had not carefully explained this possibility, he or she might think it was worse than ironic.”—Harvey Schiller MD, From the Medical Department, Watchtower Educational Center, Patterson, New York, Optimal Care for Patients Who Are Jehovah’s Witnesses, Anesthesia and Analgesia, April 2007, Vol. 104, No. 4, pp. 755-756.
answered Aug 27, 2012 by anonymous

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