Researchers have federal consent to try the drug interferon to treat West Nile virus.
The Food and Drug Administration approved the first national test. Researchers suspect interferon can lessen the symptoms and duration of the illness.
The Schering-Plough product Intron A has been shown in lab tests to be effective against West Nile.
The mosquito-borne virus is quickly spreading west from the East Coast. It has infected more than 250 people in a dozen states and caused at least 12 deaths this year.