The Centers for Disease Control and Prevention rushed 10 scientists to the region last week. In Louisiana, the state hit hardest, Gov. Mike Foster (R) has declared a state of emergency.

Much of the focus is on this swampy little town on Lake Pontchartrain across from New Orleans. Along with nearby environs, it has logged the most cases -- 18 people infected and one dead.

Throughout St. Tammany Parish, spraying has been intensive, with exhausted crews going out every night, two planes flying and the mosquito control budget already nearly exhausted. "We've increased our spraying operations three-fold, four-fold," said the parish mosquito control director, Charles Palmisano.

These efforts have helped to reassure some nervous residents here, and also to reduce the mosquito population, Palmisano said.

This weekend, many residents continued to remain nonchalant about the threat. But there also were hints of fear and some who were not taking any chances.

The thermometer was hovering around 95, but Mike Perrone was out mowing his yard, covered from head to toe in a white gardening suit. And he was covered in sweat, too. "I'd like to be out here in shorts," he said. "But with all the mosquitoes and everything, I'm out here in long sleeves."

Down a street of turn-of-the-century "gingerbread" cottages, Larry Trumbatini was outside working on his house, worrying about the mosquitoes and, with Louisiana insouciance, going shirtless. "I just watch myself come dusk," he said. "We stay indoors a lot."

Others said they were taking similar precautions, spending as little time as possible outdoors. "I don't really come out too much, to tell you the truth," Fifi Abney said. "It is kind of scary," her husband, Tom, said, emerging briefly from their house. "It's getting to the epidemic stage right now."

Officials said this weekend they had no idea why more cases of West Nile have been detected in St. Tammany than in any other parish -- East Baton Rouge, the closest competitor, has 12. "You would have to ask the birds," said the Louisiana state epidemiologist, Raoult Ratard, referring to the fact that mosquitoes transmit the virus by feeding on infected birds.

It is one of several mysteries about the epidemic, including why it has struck with such virulence this year. Ratard reiterated his prediction that "the number of cases is going to go up and up."

With such predictions in mind, some people here spoke of altering their routines, avoiding nighttime excursions or keeping insect repellent handy in their cars. "I don't even go out at night," Roy DeSilva said. "Where I stay at, we've got a lot of standing water. I stay inside, I tell you what. I can't afford to miss work. I don't want to get that sickness."

Still, the changes in behavior here are subtle and simple from people accustomed to the buzz of bugs biting.

Mosquitoes are ever present in Louisiana, as much as thick heat and violent summer downpours. Faulkner's second novel, set in New Orleans, was called simply "Mosquitoes." Yellow fever shaped local history, and mosquitoes fill the night with their whine in all seasons.

So while public officials increased their spraying and many residents heeded the call for care, many others carried on with their routine. They were out in their yards, out barbecuing, out visiting and out drinking beer on the front porch, enjoying the faint wisp of breeze from the lake.

"We're used to mosquitoes, so it doesn't really bother us," said Troy Harrison. "Because we've already been bitten so much, we don't even worry about it, until it really hits home," he said.

With 18 cases and one death -- just up the road in the village of Folsom -- you might think it had done just that. But even at the Folsom Thoroughbred Training Center, where jockey Steven Theall lived until he died last month after a two-month hospital stay, fellow jockeys and trainers were dismissive of the insect. They were not impressed by state health officials' assertions that Theall, at 53 the youngest victim, was probably finished off by the West Nile virus.

"That boy never took care of himself," said David Sullivan, a horse trainer. "He was kind of afraid of soap and water. I felt sorry for Stevie, but the boy wouldn't help himself. He caught a cold every time someone sneezed. Me personally, I don't think we have a mosquito problem," Sullivan said.

To be sure, Theall had emphysema and had suffered a stroke. But he had also been bitten by a deadly mosquito, his father, Edgar Theall, said. "He had symptoms like the flu. He just stayed weak and weak," Theall said. "The emphysema lowered his immune system."

For Felix Ardone, enjoying the shade of a massive water oak at the end of the lazy afternoon, the warnings simply meant incorporating a minor new routine. "When you wake up in the morning, you put on your after-shave, your deodorant, and you put your Cutter on," he said, referring to a brand of insect repellent. Meanwhile, on the main street downtown, families breezed in and out of a popular soda fountain, and youngsters were enjoying a ride on a vintage fire engine in familiar summer rituals even as crews prepared for another evening's spraying.

"It's got to concern people," said Tim Asher, outside the ice cream parlor. "But the attitude here is so laid-back. Mosquitoes are a way of life down here."