Federal Health Officials Alert To Threat Of New Mosquito Disease
ATLANTA -- As if West Nile virus wasn't bad enough, now U.S. health officials are on the lookout for another mosquito-bourne disease, fearing it could become a permanent part of the American landscape if it entered the country.

Rift Valley fever, which originated in Africa, is the only disease at the top of both human health and agriculture lists of dangerous diseases.

The virus can kill people, with a near 1 percent mortality rate, making it deadlier than West Nile. But Rift Valley poses a greater threat to cattle and sheep.

It kills up to 30 percent of the livestock it infects and if it were found in animals here, it would probably prompt livestock bans by other countries.

"This is not a disease that occurs here now, but we want to make sure people are aware of the signs and symptoms," said Dr. Thomas Ksiazek, chief of the special pathogens branch of the U.S. Centers for Disease Control and Prevention. "The medical and public health community need to be mindful of it."

"I think people weren't very worried about it until we started to think about agri-terror," Brown said.

The disease could appear here as mysteriously as West Nile, which first showed up as the culprit in the unexplained deaths of birds in New York in 1999.