Transfusions and transplants spread West Nile virus

From Atlanta, at a meeting of the CDC Epidemic Intelligence Service

Donated blood and organs should be screened to prevent transmission of West Nile virus, federal officials say. In addition to bites from infected mosquitoes, which is the most common route of infection in both people and animals, blood and transplanted organs can also spread the virus, two recent investigations indicate.

West Nile virus transmission has also been linked to breast-feeding, but children are less likely than older adults to get sick from the virus (See West Nile Worries Are No Reason to Give Up Breast-feeding).

Last year, the United States experienced an unprecedented 3,389 cases of human illness attributed to West Nile virus. They began on June 10 and lasted into November. In August, four people in two states became infected after receiving transplanted organs from the same donor. One of the four died.

The organ donor was infected with West Nile virus through a blood transfusion shortly before dying from an injury, Martha Iwamoto and her colleagues at CDC in Atlanta determined.

They reached this conclusion after applying two tests for West Nile virus to tissue samples from the organ donor. Tissues collected just after the donor was injured were negative for the virus, but one taken later tested positive. In the interim, the patient had received units of blood from dozens of donors.

A separate investigation identified at least 21 people nationwide who developed West Nile infections after receiving blood from infected donors. Twelve of the 21 developed West Nile meningoencephalitis, the inflammation that’s the most serious form of illness associated with the virus. Six of them died.

The donors hadn’t been diagnosed with West Nile disease when they donated blood, but they later tested positive for the virus, reports Lisa N. Pealer of CDC.

To prevent infections in the future, researchers have developed tests to identify West Nile virus in donated blood and organs for transplantation. The U.S. government could approve the tests for routine screening of blood and organs as soon as this year.

West Nile virus doesn’t cause noticeable illness in most people, but a fraction of infected people develop fever or meningoencephalitis, and about 6 percent of those who fall ill die.

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