WASHINGTON - The Food and Drug Administration on Tuesday approved a diagnostic kit that sharply reduces the time needed to test patients for West Nile virus.

The current West Nile test takes about two days and it can take up to two weeks to get results because of the large number of people tested. The new test, developed by the Australian medical diagnostics company PANBIO, only takes hours and results are available the same day, said Carl Stubbings, the company's senior vice president of U.S. operations.

The test detects antibodies to the West Nile virus in the blood. Results must be confirmed by a follow-up test, said FDA spokesman Lawrence Bachorik.

West Nile virus is a mosquito-borne disease that can cause life-threatening illness in humans, horses and birds. It was first detected in the United States in the fall of 1999. Last year, there was a record 4,000 West Nile cases in the United States.

Tuesday's announcement is timely because experts are predicting the incidence of infection from West Nile virus will rise in North America again this summer, largely as a result of a wet spring and higher mosquito populations. The disease is most prevalent during mosquito season - from July to October.

In clinical trials, the test correctly identified the antibody up to 90 to 99 percent of West Nile virus cases, the FDA said.

It was tested in four clinical sites, using more than 1,000 patients' blood serum, the FDA said.

The test will cost about $25, Stubbings said.

The federal Centers for Disease Control and Prevention said this week it has confirmed one human case of West Nile virus - in South Carolina - this year and found the virus in mosquitoes and animals in 28 states. Health officials urge that people wear insect repellent while outdoors and regularly dump water in containers, where mosquitoes breed.