DALLAS (AP) As press briefings go, the one Dallas County Health and Human Services staged May 25 was a complete bust.

It was supposed to signal the start of another mosquito season and the possible return of the West Nile virus. But nobody showed up to hear it.

Dr. Wendy Chung, the county's chief epidemiologist who tracks West Nile and other illnesses, understood the lack of media interest after two years of barely being able to detect the dreaded virus.

"There were only two cases in two years. Maybe we got lucky," she said. "Nobody could have predicted it would be as bad as it is this year."

From her quiet, orderly office on an upper floor of the health department, Chung keeps careful watch over the human dimension of the West Nile outbreak. A dozen thick binders stacked on a filing cabinet bear testimony to the epidemic's scope.

Each volume is packed with personal descriptions of the illnesses West Nile has unleashed here since June 20, the day the first human infection was confirmed.

"We have talked to everyone who has tested positive for West Nile fever or neuroinvasive disease, unless they are too ill to talk or have died," she said. "Then we talk to a family member about what happened."

Although each patient's name and other identifying information remain confidential, the rest of the information is being processed quickly to guide the local fight against West Nile.

So far, 319 West Nile cases have been confirmed in Dallas County. Most required hospitalization. The victims' ages ranged from 3 to 93. The hardest-hit age group is in their 80s, comprising 7.5 percent of the local cases.

But getting a handle on the size of the epidemic has not been as easy, Chung said. Under state law, laboratories and hospitals must report any blood test that's positive for West Nile to health authorities within seven days.

Doctors, however, aren't required to order such tests because there is no known treatment for West Nile.

Chung said the most accurate count of West Nile patients probably ends up being the sickest ones, who undergo more tests in a hospital setting. Those with less-severe symptoms, such as headaches and fever, aren't routinely tested, nor do they always seek treatment.

"By the time you find these human cases, it can be weeks after the infections occurred," she said. "That is why the government's control measures are focused on getting rid of mosquitoes, not on finding more human infections."

So far in Dallas County, 62 percent of those infected have been white, 17 percent Hispanic, 10 percent black and 11 percent "other or unknown," according to the data.

In most of the 13 West Nile deaths, underlying health problems, possibly related to advanced age, have been a contributing factor. However, a Rowlett man in his 40s was the county's most recent West Nile fatality.

Chung, who trained in pediatrics and infectious diseases at UT Southwestern Medical Center and earned a public health degree from Harvard University, said she has tried to go beyond a simple demographic overview of the evolving outbreak.

She is striving for a much deeper understanding of the trail of grief that West Nile often leaves behind.

"I'd like to draw a picture that more accurately reflects what's happening to residents of Dallas County," she said. "My role as an epidemiologist is to report the facts like a cameraman on the front lines of a war.

"I'm not fighting the battle; I'm transmitting the pictures so that it's not just a bunch of numbers at the end of the day. These are real people."

Her staff, along with a legion of volunteers, contacts every confirmed West Nile patient by phone, going through an expanded list of questions than has ever been asked.

Were they hospitalized in intensive care? Did they require intubation? Were they discharged to rehab or long-term care?

Chung said the data will give a much better understanding of the population at greatest risk not only of dying but of lingering illness from a West Nile infection.

"For every death that's reported, many others don't die, but they also don't go back to baseline, meaning they are never the same again," she said. "They face lengthy rehabilitation, and the disease will impact their lives permanently."

Chung's efforts also could shed light on how people contracted a bird virus that is mainly transmitted by mosquito bites. (Blood donations and transplanted organs have been known to transmit West Nile but are now routinely screened for it.)

The answers will guide future West Nile prevention efforts, Chung said.

Already, local physicians are latching on to the information. When they call the health department asking for treatment guidance, physicians are invited to attend a weekly briefing on the latest West Nile data, a gathering that drew 15 specialists last week.

"The doctors here have been wonderful and very perceptive," Chung said. "Ultimately, they are on the front lines."

The Centers for Disease Control and Prevention, which also tries to prevent West Nile outbreaks, has been reviewing Chung's data. It is rare, the federal agency said, to have such detailed information this early. That kind of data typically becomes available only years after an epidemic subsides.

Dr. Robert Haley, a top epidemiologist at UT Southwestern and a former CDC researcher, said Chung and her staff were doing "an excellent job" tracking the outbreak.

"She gave a presentation to the Dallas County Medical Society recently that just blew us away," he said. "It was exciting to hear they have such a detailed understanding of what's going on here."