The new test kit, manufactured by an Australian company named PANBIO, is intended for use in patients with clinical symptoms consistent with viral encephalitis or meningitis and takes only hours to make a diagnosis.

It works by detecting the levels of a particular antibody, IgM, to the disease in a patient's serum. IgM can be detected within the first few days of the onset of illness.

"This test provides a useful tool to combat the important public health problem of West Nile virus infection, just in time for the start of the West Nile season," FDA Commissioner Mark B. McClellan said in a statement.

In clinical trials involving 1,000 patients, the test correctly identified the antibody in up to 90 to 99 percent of West Nile cases, the FDA said.

Although the test is valuable in the diagnosis of West Nile virus encephalitis, the FDA cautioned that due to similarities with other viruses in the same family, the results must be confirmed by a follow-up test.

West Nile virus can be transmitted when a mosquito feeds on infected birds and then bites a human to take in blood.

While the virus often presents as a mild infection that clears without further treatment, some patients develop severe infection such as encephalitis which can result in death.

The disease is most prevalent during the peak mosquito season which is expected to begin in July and end in October. Since its first appearance in the United States in 1999, the seasonal disease has spread to 44 states. Last year, the virus struck 4,156 Americans, killing 284.

So far this year, West Nile virus has been detected in 28 US states in birds, mosquitoes and animals, and the US Centers for Disease Control and Prevention (CDC) this week confirmed the country's first human case of West Nile for 2003 in South Carolina.

(Xinhua News Agency July 10, 2003)