IRVING, Texas — With the arrival of spring rainstorms and steamy weather, mosquito-control workers in Texas and across the nation are gearing up for another round in the ongoing battle against West Nile Virus.

The mosquito-borne virus, which usually doesn’t cause serious illness but killed 177 people in the United States last year, has led health departments to change their methods for fighting mosquitoes and monitoring viruses.

In Dallas County, for example, the health department once checked dead birds and bled chickens to test for infections, but now monitors mosquito populations and possible virus problems using Global Positioning System tools.

“It’s reawakened our public, our politicians and us to the importance of mosquito control,” Texas A&M University entomologist Jim Olson told North Texas health department workers this week.

Texas, where the virus first appeared in 2002, led the nation in West Nile deaths last year with 32. The state’s 354 human cases was second only to Idaho’s 996, according to the Centers for Disease Control and Prevention.

West Nile was detected in the United States in 1999 in New York. Mosquitoes spread the virus by contracting it from infected birds and then biting other birds or animals. Among mammals, humans and horses are the most commonly sickened.

The virus spread across the lower 48 states by 2005, but it’s too early to say where it will be most active this summer. Two human cases have been reported this year, both in Mississippi, according to that state’s health department. The Texas health department reports one horse case this year, in Collin County.

“We can certainly guess that people are going to be at risk in all parts of the U.S.,” said Emily Zielinski-Gutierrez, a behavioral scientist at the CDC Division of Vector-Borne Infectious Diseases in Fort Collins, Colo.

In Texas, the cold winter slowed reproduction of two mosquito species mostly responsible for West Nile in the state, Olson said. Recent flooding also disrupted the carrier species, although it triggered an abundance of other annoying mosquito species.

“Now we’re going into bird-nesting time, which is the prime buildup time for the bird and mosquito populations,” he said. “The juvenile birds are the most vulnerable to mosquitoes and lack any kind of immunity, and the virus explodes in them.”

Olson said a recent Texas A&M survey covering Houston and Bryan found that the public is aware of West Nile prevention measures, such as eliminating stagnant water, but that hasn’t translated into action.

“John Q. Citizen thinks if they pay their taxes, then you ought to get rid of the mosquitoes,” he said.

That’s the task facing Scott Sawlis, vector control supervisor for Dallas County, which last year confirmed 59 human cases of neuroinvasive West Nile — the form of the disease that can cause meningitis or encephalitis.

Dallas County opened a mosquito-testing lab in 2004 and is working with local municipalities to implement weekly mosquito collection at 30 permanent traps. The information will be posted on the Web. Sawlis said the program will build an index of species and locations as well as enable the county to act quickly with insecticide.

Zielinski-Gutierrez said West Nile brought renewed government and academic resources to mosquito-control that make programs like Dallas County’s possible.

But the multitude of factors affecting West Nile outbreaks makes it difficult to predict if the disease will ever be controlled. The virus’ eight years in the U.S. isn’t enough time for reliable patterns, she said.

“West Nile is not going to go away,” Zielinski-Gutierrez said. “As it fades from the headlines and it’s not as present, the challenge is going to be to maintain the resources … to handle mosquito control effectively.”

On the Net:

CDC West Nile page,

Texas Department of Health West Nile page,

The More You Know: Facts About West Nile Virus

(AP) — Health officials say most people infected with West Nile Virus show no symptoms. About 20 percent of cases result in West Nile fever. Less than 1 percent of infections result in severe cases of neuroinvasive West Nile, which can cause encephalitis and meningitis.

Symptoms of West Nile Fever:

fever headache nausea sore throat body aches fatigue skin rash swollen lymph glands

Symptoms of

neuroinvasive West Nile Virus:

headache high fever stiff neck disorientation tremors convulsions muscle weakness coma paralysis numbness permanent neurological effects

Tips for avoiding West Nile Virus:

Apply insect repellent to exposed skin and clothing Wear long sleeves and long pants outdoors Stay indoors at dusk and dawn, when mosquitoes carrying the virus are most active Drain standing water from places such as flower pots, old tires and rain gutters.

Sources: Texas Department of State Health Cervices, Centers for Disease Control and Prevention.