Officials Believe Woman Had Encephalitis : Public health: Pending test results may confirm that the county has had its first human case of the disease’s St. Louis strain.

State health officials have turned up what is believed to be the first human case of the St. Louis encephalitis virus in Ventura County.

But officials are awaiting the results of another test before making the confirmation final.

“It’s not 100% confirmed yet,” Ventura County public health officer Dr. Larry Dodds said Tuesday.

The mosquito-borne encephalitis virus causes symptoms similar to the flu, including fever and nausea. In more severe cases, it can cause brain damage or death.

Doctors strongly suspect that a 70-year-old Oxnard woman who was hospitalized in early September complaining of disorientation, severe headaches and other flu-like symptoms may have had the disease, Dodds said.

Her illness was not reported to the public health department until mid-October, he said.

Health officials do not know how the woman may have contracted the virus, but are attempting to find her for further questioning. She was released from the hospital and later moved out of the county, an official said. Neither she nor the hospital was identified.

The Ventura County case is one of two that have been reported to state health officials this year, said Robert A. Murray, deputy epidemiologist for the infectious disease branch of the state Department of Health Services.

The other case was reported in August in the El Monte area of Los Angeles County. Murray said additional Ventura County residents may be infected.

“For every case of this illness that is identified, hospitalized and diagnosed, there could be . . . up to 100 people who are infected,” he said. “The illness is more likely to be recognized the older a person is.”

The virus is found in the blood of wild and domestic birds. Once mosquitoes feed on the infected birds, they can carry the virus to humans. However, the virus cannot be transferred from person to person or from birds to people, officials said.

Bob Gallagher, who manages the county’s encephalitis virus program, said county residents have little to fear because the number of mosquitoes is declining with the onset of colder weather.

“We don’t want to cause a panic,” he said. “It becomes less and less likely that the type of mosquito that can transmit encephalitis is going to be around biting people.”

The last time the state reported an epidemic of encephalitis was in 1989, when there were 29 cases. None of the victims died that year.

Before that, an epidemic hit Southern California in 1984. That year, the state recorded 26 cases, 16 in Los Angeles County. One of the victims died.

“California is an area that is endemic for mosquito-borne encephalitis,” Murray said. “It certainly is something we do have to be on guard for.”

Meanwhile, county environmental health officials stepped up a program to monitor the spread of the virus.

Health officials are concerned that the mosquito-borne virus may already have spread to other parts of the county, Gallagher said.

One of three flocks of chickens that serve as an early warning system for the county has shown signs of infection. Routine testing last month indicated that two of 10 chickens in a flock located in Thousand Oaks had been infected, probably from a mosquito.

Two other flocks located in Simi Valley and in Fillmore have shown no signs of infection.

“We have evidence from both the positive chickens and now a possible positive human,” Gallagher said. “It’s a pretty strong indication that we have wild birds in parts of Ventura County that act as a reservoir for the St. Louis encephalitis virus.”

Workers began trapping wild birds, such as sparrows and finches, in the Oxnard area this week.

Their blood will be drawn and analyzed to determine whether they also are infected with the virus. The trapping is expected to continue into the spring, Gallagher said.