The probable case comes after Friday's announcement that a young woman who lives in the southwestern part of the county very likely contracted viral meningitis from a West Nile virus. If her diagnosis is confirmed, she would represent the first human case of West Nile acquired west of the Rocky Mountains.

Lab tests for West Nile were inconclusive for a third person, a young Las Vegas woman hospitalized in Los Angeles for encephalitis, an inflammation of the brain that can be caused by West Nile. The woman had recently traveled to the Houston area, although health officials do not know if her trip fell within the West Nile incubation period of three to 14 days.

[Jonathan Fielding] said additional tests are required in all three cases before a final diagnosis can be made. The tests will look for the presence of antibodies to West Nile and rule out other types of infection.