CDC Continues to Track West Nile Virus in United States

The Centers for Disease Control and Prevention (CDC) continues to work with state and local health departments to help control West Nile Virus (WNV). To date there have been a total of 854 human cases of WNV infection reported to CDC from 28 states, the District of Columbia and New York City. There have been 43 fatalities reported.

CDC expects many more cases of West Nile Virus infection to be reported in the coming weeks as the transmission season peaks in different parts of the country. Exposure to WNV through a mosquito bite is the principal means of acquiring infection. CDC continues to urge people to take steps to protect themselves from being bitten by mosquitoes. These steps include eliminating standing water from around the home where mosquitoes are likely to breed, wearing long sleeves and pants, and wearing insect repellents that contain DEET.

In addition, the agency continues to work with the Food and Drug Administration (FDA), Health Resources and Services Administration (HRSA), and the Georgia and Florida departments of health to investigate a cluster of cases of WNV infection through transplantation of organs from one donor. So far, three people who received organs from a single donor have been diagnosed with encephalitis due to WNV; one has died and the other two are recovering in the hospital. Also, today a fourth organ recipient has tested positive by the Florida Department of Health Bureau of Laboratories and has been diagnosed with WNV fever - a milder form of the infection.

Testing of the organ donor demonstrated evidence of West Nile virus

infection from samples taken at the time of death. The means of the donor's infection remains under investigation; it is most likely that the donor became infected with the West Nile virus through a mosquito bite or via blood transfusion shortly before organ donation.

As a precaution, remaining blood products from donors of blood given to the organ donor as well as to the organ recipients have been voluntarily withdrawn from use. Donors of blood given to the organ donor will be contacted to be tested for West Nile virus. Recipients of blood products from these donors will also be contacted and tested for West Nile virus. The CDC, FDA, Georgia and Florida state health departments, HRSA, and blood collection agencies are working together to identify the source of the organ donor's infection.

CDC is also investigating a case of WNV infection in a Mississippi resident diagnosed nearly four weeks after receipt of multiple units of blood associated with a surgical procedure. The patient reported having been bitten by mosquitoes on numerous occasions prior to hospitalization. However, as a precaution, remaining blood products from donors of blood to the patient have been voluntarily withdrawn from use. Preparations are underway to contact donors of blood given to the patient so testing for WNV can be done. Similarly, recipients of blood components from these donors will also be contacted and tested for WNV.

A large of number of WNV infections as a result of a mosquito bite are occurring in the United States. By chance alone, some of these persons will have received blood transfusions. Recent receipt of a blood transfusion by a person with WNV infection does not necessarily implicate the transfusion as the source of infection. CDC will be working with states reporting cases similar to the one in Mississippi to learn more about the likelihood of WNV transmission through blood.

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