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Fact Sheet

Fact Sheet: West Nile Virus Infection in Organ Transplantation and Blood Transfusion Recipients

WNV Investigation Update

  • CDC in concert with other HHS agencies (FDA, HRSA) and blood collection agencies continues its investigation into the risks of transmission of WNV through blood transfusions and transplanted organs
  • An initial investigation in Georgia and Florida confirms WNV transmission from the transplanted organs of a single donor to four recipients
  • Additionally, five investigations of the possible role of WNV transmission through blood transfusion, and one other involving both organ transplantation and blood transfusion are being reported today. Each of these instances has been reported in areas where natural mosquito borne transmission of WNV also occurs
  • One of these five, involving the case of a Mississippi patient, who developed WNV meningitis within several weeks after blood transfusion is highly suggestive of infection via WNV containing blood
  •  Blood samples (obtained at the time of donation) from 15 of 17 donors were tested and WNV genetic material was identified in samples from three donors
  • Follow-up investigation of one of those three reveals the donor sought medical care four days after donation because of fever, chills and headaches—all symptoms consistent with WNV infection. Follow-up WNV antibody testing of this donor is in progress
  • Live WNV grown from a blood product (frozen plasma) taken from this donor, establishes that WNV can survive in some stored blood products. This finding demonstrates that WNV can likely be transmitted by transfusion but does not prove this route of transmission. In this case the blood recipient who developed WNV was exposed to mosquitoes and lived in an area where WNV was active, so natural exposure cannot be ruled out

Next Steps

To better assess the risk of WNV transmission through blood transfusion or organ transplant, in cooperation with the blood banking community, hospitals, and health departments, the CDC and FDA are taking these steps:

  • Investigating the cases of individuals with confirmed WNV who are reported to have received blood transfusion or organ transplants in the weeks preceding their WNV diagnosis.
  • Developing a survey of blood samples routinely collected at the time of blood donation, to determine the prevalence of WNV in the blood of donors in geographic areas of high, moderate, and low WNV activity

CDC and FDA are also taking precautionary measures to reduce the risk of WNV transmission by blood transfusion or organ transplantation:

  • Unused blood components from donors of blood given to persons who developed WNV infection after transfusion are being withdrawn
  • CDC has requested that health departments seek to identify those individuals with WNV infection who received recent blood transfusions or organ transplants prior to their WNV diagnosis and to then investigate such cases; Additionally, persons with WNV infection will be asked whether they donated blood prior to their illness so that unused blood from prior donations can be withdrawn and recipients can be enrolled in studies.
  • FDA, which is responsible for blood safety, has begun work with public and private partners to speed development of WNV tests suitable for blood donor screening, to prepare for the likely possibility that such testing may be needed
  • FDA is assisting blood centers in developing guidelines to enhance the reporting of post-donation illnesses suggestive of WNV infection and determining when withdrawal of blood and blood products from such donors is warranted
  • FDA is evaluating potential approaches to permit investigational use of blood products treated to inactivate viruses using methods currently in development.

The discovery that WNV may spread through blood transfusions and organ transplants comes at a time of seasonal decline in natural WNV activity, although year-round activity may persist in warmer parts of the country.

Advice for Patients, the Medical Community, and Blood Centers

CDC and FDA recognize the public health implications relative to the apparent transmissibility of WNV by blood transfusion and organ transplantation.

  • There is absolutely no risk of acquiring WNV by donating blood. The health and well being of thousands of people in the U.S. require adequate supplies of blood and blood products. Blood donors are encouraged to continue donating blood as usual.
  • There apparently is some risk of acquiring WNV infection by blood transfusion or organ transplantation. That risk is currently believed to be low. However, additional studies are needed to quantify that risk and are being developed. Pending the results of these studies, clinicians and their patients must consider the immediate benefits of transfusion or transplantation.
  • In emergency situations and other settings where blood transfusion and organ transplants may be lifesaving, the benefits of blood transfusion and organ transplantation outweigh the risk of WNV infection
  • In elective situations, medical decisions about transfusion should take into account the personal preferences and concerns of individual patients and their health care providers. Options may include deferral of elective procedure or, in some instances, use of autologous (self) blood transfusions.

Bites from mosquitoes carrying WNV remain, by far, the most common means of transmission. Persons living in areas where WNV remains active should observe precautions to minimize exposure

  • When possible wear loose fitting clothing that covers legs and arms while in areas where mosquitoes are likely to be present
  • Apply insect repellant containing DEET
  • Avoid outdoor activities during dusk, or other times when mosquito activity is greatest
  • Assure that window and door screens are in good repair and that other routes of mosquito access to buildings and living space are blocked


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This page last updated September 19, 2002

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