SEATTLE (AP) - The mysterious illness that killed the Woodland Park Zoo's youngest elephant, Hansa, last month was a previously undiscovered type of "elephant herpes," zoo officials said Monday.

The disease, which attacked her blood vessels, varied genetically from the types of herpes that have been known to infect Asian and African elephants, scientists determined.

Hansa, who had been one of the zoo's star attractions since her birth in November 2000, suffered a drop in activity and appetite beginning May 31. Her handlers monitored her closely and administered fluids and antibiotics, but she was found dead in her stall June 8. Samples of her blood, tissue and organs were sent to scientists around the country in hopes of learning what killed her.

"We were still pretty sad but grateful to find out the cause," deputy zoo director Bruce Bohnke said Monday. "It gives us some closure."

Zoo officials said they don't know how long Hansa had the herpes, but it could have been since birth. Without a test for the illness, they also don't know whether it might have spread to the zoo's other elephants: Hansa's mother, Chai, 28; Bamboo, a 40-year-old Asian elephant; and Watoto, a 38-year-old African elephant.

Since 1983, there have been 18 cases of previously known types of elephant herpes in the United States, some proving fatal within a day.