Aug. 30 (HealthDay News) -- A new test to detect the West Nile virus in donated blood and organs has been approved by the U.S. Food and Drug Administration.

Roche's cobas TaqScreen WVN test uses nucleic acid technology to detect the virus even before the donor's body begins to produce antibodies or show symptoms of infection, the agency said in a statement. The test is not intended to diagnose West Nile in non-donors.

Most people with West Nile show no symptoms, but in rare cases serious symptoms may develop including brain inflammation, headache, high fever, neck stiffness, stupor, disorientation, coma, convulsions, muscle weakness, and paralysis. People with compromised immune systems are more susceptible to the more serious infections with West Nile.

The virus is most often transmitted by infected mosquitoes, but it can also be passed from person to person by blood transfusion or organ transplant.

Since the virus first appeared in the United States in 1999, as many as 3 million cases have been reported to the U.S. Centers for Disease Control and Prevention.