Fairfax County health officials said an elderly man has died of a suspected case of West Nile virus. If additional tests confirm the diagnosis, his death will be the first reported fatality from the virus in Virginia this year.

The patient, from the county's Mount Vernon District, developed symptoms last month. Humans most often contract West Nile virus from a mosquito bite but almost never develop symptoms. The victim, whose name and age were not released by health officials, developed a more serious condition, which they say contributed to his death.

Laboratory samples from the victim are being sent to the Center for Disease Control and Prevention for confirmation. Results may take several weeks.

Most people who get West Nile virus suffer no symptoms or a mild flulike illness and recover without treatment. In a few people, mostly older than 50, the virus can cause serious illness such as encephalitis or meningitis.

State and local health officials in Virginia are characterizing this year's West Nile virus as "relatively quiet," and one that has resulted in a fraction of the suspected human cases of West Nile reported in 2003.

At this time last year, the state had reports of 24 suspected human cases of the virus. So far this year, there have been five across the state. "West Nile virus has not been as active in Virginia this year," said Virginia Department of Health spokeswoman Lucy Caldwell.

Fewer infected mosquitoes and birds have been identified, officials said. Last year, Fairfax residents reported 1,250 dead birds, 15 of which were found to be infected with West Nile. This year, officials said reports of dead birds have dropped dramatically to several hundred. Fewer birds have been tested this year, and only three of those have tested positive for West Nile in Fairfax.

The rate of infection among mosquitoes in Fairfax has also plummeted, from 20 to 30 infected mosquitoes per 1,000 collected to about five per 1,000, officials said.

Officials said this is the first year they've had good baseline data to examine the problem in Fairfax. Aggressive public outreach programs may be having an impact, officials said. The bird population also may be playing a role. Birds that were infected have either died or become immune, officials said.

Even the wet weather may have contributed, officials said, washing mosquito larvae out of storm sewers before they could mature.

Still, officials warned that it's impossible to know where the infection trend is headed.

West Nile "came into the United States in 1999, and it has gone across the continent like a wave," said Jorge Arias, who is the West Nile virus program supervisor in Fairfax County. "It peaks and it goes down. We don't know if there's a second wave behind it. We don't know what will happen over time."

Virginia's acting state epidemiologist, Suzanne Jenkins, agreed.

"We can certainly theorize [on the lower numbers], but we can't prove anything," Jenkins said. "It's probably a combination of things."

Therefore, officials continue to urge residents to be careful to eliminate mosquito breeding areas around their homes and use DEET-based repellents.

"There's no reason to get super excited, and I wouldn't become complacent," Jenkins said. "The mosquito season is not over, and there's always next year."