An Okinawa woman who had been suspected of having contracted the West Nile encephalitis virus is probably not infected, the Health, Labor and Welfare Ministry said Monday.

The National Institute of Infectious Diseases in Tokyo has been conducting tests on the 42-year-old woman, who complained of fever, headache, vomiting and drowsiness after returning July 31 from the United States.

The institute has conducted genetic and antibody tests on her blood and spinal fluid but could not confirm any evidence of the virus, according to the ministry.

She was also suspected of having been infected with the Japanese encephalitis virus. But the institute's tests have likewise found her negative for this virus.