The virus is a bird pathogen and is not likely to jump the species barrier to cause infections in humans. However, state health officials are taking no chances and scientists at Wadsworth Laboratory, a division of the State Health Department, are studying the virus.

State wildlife pathologist Ward Stone, who was instrumental nearly a decade ago in identifying the pathogen that turned out to be the West Nile virus, said the sudden sweep of death among crows has caught scientists by surprise.

"Initially, I didn't know what it was," Stone told Newsday Thursday. "You really don't know until you do the post-mortem examinations," he said, which include preliminary viral typing. Additional specimens are being sent to a federal wildlife laboratory in Madison, Wis., which is expected to provide further molecular details about the strain.