FDA approves cobas TaqScreen WNV test for West Nile virus

The U.S. Food and Drug Administration has announced approval of a second test for the detection of West Nile virus (WNV) in blood and organs.

The cobas TaqScreen WNV test is an automated test that's able to detect the genetic material of the virus itself early in the infection. Such nucleic acid testing improves blood and organ safety, detecting whether donated blood and organs have been infected even before the donor's body has begun to produce antibodies against the virus.

Most often, WNV is transmitted to humans by mosquitoes. But WNV can also be transmitted by blood transfusion or organ transplantation from infected donors. While WNV infection is common in Africa, Asia, and the Middle East, it did not appear in the United States until 1999. Since then, WNV has become endemic in most of this country, with from 1 million to 3 million cases between 1999 and 2006, according to the Centers for Disease Control and Prevention.

"This action is the culmination of the dedicated efforts of FDA, our sister agencies, blood establishments, and manufacturers to bring donor screening tests to market for this increasingly common virus," said Jesse L. Goodman, M.D., M.P.H., director of FDA's Center for Biologics Evaluation and Research. "As a result, blood centers and hospitals now have a choice of two FDA approved tests to screen for West Nile Virus in donated blood and organs."

Most people infected with WNV show no signs of the disease but about 1 in 150 to 1 in 350 infected people will develop serious symptoms, including encephalitis, an inflammation of the brain. Since the introduction of the virus, the reported number of human cases of serious WNV in the United States has grown steadily from 62 in 1999 to 4,269 in 2006.

WNV has been especially virulent this year. Although it is still early in the WNV season, 58 blood donors who are possibly positive for the virus have been reported to the CDC as of August 21, 2007.

The cobas TaqScreen WNV test is approved for the detection of the virus in plasma specimens from human donors of whole blood and blood components (plasma, red or white cells, platelets) and living donors of cells, reproductive cells and other tissues. It is also intended for use in testing plasma specimens of organ donors when specimens are obtained while the donor's heart is still beating. The test is not intended for use on samples of cord blood or as an aid in the diagnosis of WNV infection.

Approval comes as FDA is preparing guidance on the use of licensed WNV screening tests for blood donors.

The test is manufactured by Roche Molecular Systems Inc. of Pleasanton, Calif.