This year's big threat

Dry weather draws West Nile virus to Valley urban areas as human cases rise.
By Denny Boyles / The Fresno Bee
08/11/07 04:31:54

This year's dry conditions were supposed to spell relief from the West Nile virus. Instead, the disease has thrived in the San Joaquin Valley.
Birds and mosquitoes in search of scarce water have found it in urban areas. The result: concentrated breeding grounds for West Nile right where people live. Six have died statewide so far.

That's not what health and mosquito experts expected after lower-than-average rainfall and a smaller-than-normal snowpack.

"We couldn't have been more wrong," said Gene Abbott, a superintendent for the Kern Mosquito Abatement and Vector Control District. "Instead of seeing fewer West Nile cases, we've actually seen an increase because the drought has driven the birds, and the mosquitoes, closer to our population centers."

West Nile virus is a neuroinvasive disease that most often is spread by mosquitoes as they feed on birds, horses and humans.

Most who contract the virus do not show signs of the disease, but some can become seriously ill with flulike symptoms. About 20% who contract the disease develop symptoms, and a small percentage can die.

The disease first appeared in the United States in 2000, and spread to the West Coast within a few years. West Nile cases typically peak within two or three years of their first appearance in a region, then begin to taper off as birds develop immunity.

In California, West Nile peaked in 2004, with 779 human cases and 28 deaths. The number of human cases and deaths has dropped steadily each year -- until this year.

Statewide, there are now three times as many West Nile cases this year compared with last. Through Aug. 2, California had 56 confirmed human cases, compared with 20 for the same time period in 2006. As of Aug. 7, the count had risen to 75 confirmed human infections.

Officials also are concerned about where the cases are occurring.

In the past, human cases of West Nile usually have been in rural areas, near farmland, rivers or lakes, Abbott said. But the water shortage has forced birds and mosquitoes to seek out ponding basins, riverbeds in city areas and even swimming pools. In Kern County, that has meant that this year the majority of human cases are in Bakersfield.

That has put Abbott and his fellow mosquito fighters at the center of California's fight against West Nile this year.

So far in 2007, Kern has had 48 confirmed cases of West Nile in humans, just one below its total for all of 2006, and far more than any other county in the state. Kern also has had two deaths, which prompted Gov. Schwarzenegger to include Kern in a state of emergency declaration last week that also includes Kings, Glenn, Colusa and San Joaquin counties. Each of the other counties has had one death.

The declaration will pump more than $1 million for mosquito abatement into those counties, and also help fund education efforts to remind people that West Nile is here to stay.

"West Nile isn't going anywhere, it's just a matter of how bad it will be from year to year," said Tim Phillips, assistant manager of the Fresno Mosquito and Vector Control District. "This year, because of a lot of different factors, it's been bad."

Experts said West Nile is more prevalent in warm areas such as the Central Valley because the heat seems to drive the infection in birds and mosquitoes.

This year, additional factors are contributing to the problem. Abbott, in Kern County, said those factors include hundreds of abandoned and repossessed homes, many of which have swimming pools that have turned into green mosquito hatcheries.

"In June alone, Kern County had 800 home foreclosures," Abbott said. "We're working with the Realtors to get a list of which homes had pools, but for now we are relying on the public. When they let us know about a green pool, we can treat it, and at least reduce the threat a little."

Kern County has recorded more than nine times as many cases as Fresno, which comes in a distant second with five human cases.

Abbott said he can't explain why, but he suspects Fresno has many undiagnosed cases.

"Look at the numbers," Abbott said. "We've had 89 dead birds test positive, and Fresno County has had 77. They should be closer to us in human cases based on that. Maybe they have a lot of cases that just haven't been diagnosed."

Diagnosing West Nile can take time, something Frances Navarette knows all too well. Navarette, a 61-year-old retired science teacher from Fresno, suffered through what she and doctors thought were severe flu symptoms for two weeks before it was confirmed that she had West Nile.

"It's been hell," Navarette said. "It attacks your system like nothing else. I was hospitalized for a week and still get dizzy or nauseous when I stand up sometimes."

Navarette, who was active and healthy before catching West Nile, hopes her experience will help others by encouraging them to not only take preventive measures to avoid mosquito bites, but also encourage their doctors to test for West Nile if they have flulike symptoms.

Navarette isn't sure how she was infected with West Nile. She spends a lot of time outdoors, and is an avid gardener, but wears mosquito repellent that she thought would protect her.

"I never believed I would get West Nile, but I did," Navarette said. "People really need to keep an open mind, and encourage their doctors to do the same. This disease is real here. You can catch it."

The reporter can be reached at dboyles@fresnobee.comor (559) 441-6659.