Testing Finds Blood Donors Are Carrying Nile Virus

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http://www.nytimes.com/2003/09/19/science/19NILE.html?th

 

Testing Finds Blood Donors Are Carrying Nile VirusBy LAWRENCE K. ALTMAN

 

 

Anew test has detected the West Nile virus in more than 600 blood donors across

the country this summer, preventing transfusions of the contaminated blood,

federal health officials said yesterday.

 

The figure may rise because infections from the virus, a mosquito-borne disease,

continue, although the season appears to have passed its peak, the officials

said.

 

There is no way to be sure precisely how many West Nile cases were prevented by

the test to screen donations, because scientists do not know what proportion of

the recipients of the contaminated blood became ill, the officials said.

 

Because each unit of donated blood is broken into components and transfused into

about two patients on average and the percentage of patients who have received

contaminated blood is very high, the screening tests seem to have prevented a

significant amount of illness, the officials said.

 

" We can presume that we've prevented a very large number of infections and some

significant amount of clinical disease, " Dr. Jesse Goodman, an official of the

Food and Drug Administration in Washington, said.

 

Two patients who received transfusions did contract West Nile encephalitis, or

inflammation of the brain, this summer, the Centers for Disease Control and

Prevention in Atlanta said. In one case, the tests failed to detect the virus.

Officials said they were not certain how the other case occurred.

 

The director of the centers, Dr. Julie L. Gerberding, said in a news conference

yesterday that although the new test was " a major step forward in protecting the

nation's blood supply, " the two cases that slipped through the system showed

that " it's not perfect. "

 

Dr. Gerberding cautioned doctors to consider West Nile fever in patients who

experienced headaches and fevers after transfusions.

 

The first West Nile case in the Western Hemisphere was detected in 1999, in New

York City. Critics say federal officials and infectious disease experts were

complacent about the possibility that the virus could be transmitted through

transfusions.

 

Last year, 23 patients acquired West Nile through transfusions, researchers from

the federal government and the Michigan Department of Community Health and the

American Red Cross reported in The New England Journal of Medicine.

 

After transfusion-associated cases of West Nile were first identified last year,

federal officials said they realized the need for a test to screen the blood.

Blood banks asked donors about symptoms of recent illnesses. But the West Nile

virus can be present in blood before symptoms develop or even among people who

report few, if any, symptoms.

 

The F.D.A., blood banks and the biotechnology industry collaborated to develop a

test that has been used in blood banks since late June.

 

The test detects the genetic signature of the virus. But because its development

was rushed, manufacturers could not produce enough so that blood banks could use

it to test each unit of donor blood, Dr. Gerberding said.

 

So blood banks generally take a sample of the blood from each donor, mix it with

blood from 6 to 16 other donors and test the pooled sample. If the test

indicates the presence of virus, blood banks then test each donor's blood.

 

But in some areas where West Nile is particularly prevalent this summer, blood

banks are testing each donor's blood. Those states include Kansas, Nebraska,

North Dakota, Oklahoma and South Dakota, Dr. Gerberding said.

 

The test, which also helps doctors diagnose West Nile fever, has led to more

milder cases being reported than in the past, Dr. Gerberding said. But, she also

said, more cases of encephalitis are being reported this summer.

 

This year, 4,137 human cases of West Nile fever have been reported nationwide.

Colorado has reported the most cases, 1,542, followed by South Dakota, 580;

Nebraska, 554; Wyoming, 282; and Texas, 276.

 

 

 

 

 

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