Not long ago, before anthrax and severe acute respiratory syndrome surfaced as public health issues, the Washington area focused on a potentially fatal virus with a somewhat exotic name: West Nile.

Now, four years after the illness was first detected in the United States, officials are preparing for what has become an annual effort to chart and curtail the spread of the virus that last year killed 11 people in Maryland, Virginia and the District.

That effort -- detecting the spread of West Nile in humans, birds and mammals, as well as curtailing the growth of culex mosquitoes carrying it -- is expected to be more challenging than ever. Last year, as the number of deaths tied to the virus grew, West Nile also spread from such population centers as the Baltimore and Washington suburbs to Maryland's Eastern Shore and other rural areas.

That means West Nile has moved to where the mosquitoes are.

And that development -- coupled with prime breeding conditions left by a wet winter -- has some experts concerned. Mosquito-dense areas in Louisiana, for example, were hard hit by the virus, which produced 29 deaths and 329 confirmed cases in the state in 2002, according to the federal Centers for Disease Control and Prevention.

"We're concerned that this year we're going to have a great more difficult time in mosquito control related to West Nile than we did in the past," said Cyrus R. Lesser, chief of the Maryland Department of Agriculture's mosquito control section.

The good news is that officials feel better prepared to handle it. Rural areas where West Nile has arrived already have extensive mosquito control programs. And suburban communities that never engaged in organized mosquito control before West Nile are now doing so, Lesser said.

State and local health departments say they will be equipped to do a better job of detecting the spread of West Nile. More counties are hiring entomologists or biologists, so the state "will have more localities doing mosquito surveillance," said Suzanne Jenkins, an assistant state epidemiologist in Virginia.

The state is also more ready to help the counties in the effort to stem the spread of West Nile. With an infusion of federal dollars earmarked for bioterrorism prevention, Virginia has been able to hire more epidemiologists across the state.

"They're going to help us in looking for West Nile virus cases," Jenkins said.

Compilation of West Nile data has become more and more detailed since the disease was detected in crows in 1999.

Last year, Virginia reported West Nile virus in 933 birds, 45 horses and nine people -- two of whom died. In Maryland, 604 birds and 30 horses tested positive for West Nile last year, along with 36 people, seven of whom died. The District reported that 161 birds and 14 people tested positive for West Nile. Two of the people died.

Health officials in the three jurisdictions also charted mosquito "pools" that tested positive for West Nile: Maryland had 46 pools, the District 81 and Virginia 180.

Detection of the virus helps officials determine where to attack it. For example, after it was determined that mosquitoes were breeding in storm sewers in a part of Richmond, larvicides were put in the drainage sites, Jenkins said.

"We like to believe we prevented some human cases," Jenkins said.

Similar efforts have been made in other areas. Officials have persuaded locales to do a better job of policing storm retention ponds or building them in such a way that they drain after a short time.

The National Zoo in Washington has also taken measures this year to clear standing water and inoculate birds with an equine vaccine believed to act on West Nile.

The battle plan stems from the detection of West Nile at the zoo, first in dead crows in 2001, then in birds housed on the grounds last year. Associate pathologist Donald K. Nichols said approximately 20 zoo birds were lost last year because of West Nile. West Nile was also detected in a gray seal that died.

"The cause of the death was the heart failure, but the West Nile kind of finished it off," Nichols said.

Zoo officials are "kind of concerned that this really might be a really bad mosquito year," he said, because of all the standing water, but they are hopeful that the problem with West Nile will lessen, as it has at other affected zoos.

"It seems like the first year it hits, it's really bad," Nichols said. "We're hoping that last year was our bad year."

Officials in the District and Maryland have said they are nearing completion of a blueprint for West Nile surveillance this year.

If Virginia is any example, the surveillance will change from years past.

The state is "not testing as many birds," for example, and will stop collecting samples in certain areas "once a certain number is reached," Jenkins said.

"We're not looking for the first West Nile in Virginia this year," Jenkins said. "We know it's here."

The same goes for Maryland, which hopes to initiate its surveillance program next month. But it will no longer do emergency spraying for mosquitoes after the virus is detected. It is simply not effective, officials say.

"It's endemic. It's part of the environment we have to live with," Lesser said.

The tips that health officials are offering to residents are largely the same: Wear insect repellant when outside, and remove standing water from around homes.

Kimberly Mitchell, Maryland's West Nile virus coordinator, said "the primary mode of transmission is still through the bite of a mosquito," though she said cases nationwide last year showed that the virus can spread through organ transplantations and transfusions and from mother to fetus.

Mitchell pointed out that mosquito control can go only so far before it begins to damage the environment.

"I think a common myth is that people can completely eradicate West Nile by killing all the birds, killing all the mosquitoes," she said.

Officials also have to weigh the danger to humans. Mitchell said that "it's only in very rare instances that people develop very severe symptoms." Most people experience "no symptoms at all, or mild symptoms," like a "headache or sore throat or body ache," which pass in two weeks or so, she said.

"In less than 1 percent of cases do people develop severe symptoms and have to be hospitalized," Mitchell said.

All the deaths in Virginia and Maryland last year occurred in people 50 or older.

"Right now, there is no vaccine available for humans," Mitchell said.

Maryland will still operate a West Nile hotline, this year at 866-866-CROW. But it's a sign of the times that, despite a telephone number that was picked when a dead crow was cause for panic, the hotline is now meant for reports of all "hot topics," such as bioterrorism.

Officials know that West Nile virus is here -- and likely to stay.

"It's going to come back every year," Mitchell said.