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ATLANTA — As if West Nile virus wasn’t bad enough, U.S. health officials are fearful of another mosquito-borne disease that could enter the country.

Rift Valley fever, which originated in Africa and hasn’t been seen outside that continent since 2001, can kill people.

It has a near 1 percent mortality rate, deadlier than West Nile.

But it poses a greater threat to livestock, killing up to 30 percent of those infected.

“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 of the U.S. Centers for Disease Control and Prevention.

Most people get a flu-like illness when infected. Some may develop serious symptoms, including liver or kidney disease, Ksiazek said.

About 14 percent of those seriously ill with Rift Valley fever have died.