Virus linked to foreclosures

One of the nation’s worst-hit cities for foreclosures in 2007 -- Bakersfield -- became an epicenter of West Nile virus that year largely because of mosquitoes breeding in abandoned swimming pools, UC Davis and Kern County scientists reported Thursday.

The Central Valley city had 140 diagnosed cases, up from 51 in 2006, or a 275% increase. Over the same period, mortgage delinquency notices went up by 300%.

Since the mortgage crisis began, public health officials throughout the state, particularly in Southern California, have complained that neglected pools are contributing to West Nile infections.

But the Bakersfield study, published in the online journal Emerging Infectious Diseases, was the first to quantify the effect.

Other factors played a role. Unusually mild weather allowed virus-carrying mosquitoes to survive the winter, the study found. And mosquitoes became active earlier and multiplied more rapidly in an exceptionally warm spring and summer.

By the time public health officials noticed the first human case, the virus had exploded.

“Once we had one human case, it was almost like popcorn after that,” said Dr. Claudia Jonah, Kern County’s interim health officer. “In a year in which we should not have had any cases, we had the most in the nation.”

The exceptionally dry winter and spring had initially been expected to cut down on the number of mosquitoes. But, in fact, the drought contributed to the problem, the study found, drawing birds to the suburbs in search of water. The birds found thousands of stagnant pools, teeming with newly hatched mosquitoes.

West Nile is primarily a bird disease, transmitted among birds -- and to humans -- by mosquitoes. Most people who are infected by the virus do not become ill. But about 20% of those infected develop flu-like symptoms, and about one in 150 develop the most serious form of the disease, which can cause encephalitis, meningitis and death.

Aerial photographs taken over Bakersfield in July 2007 showed hundreds of suburban backyard pools with green instead of blue water, evidence that the pools were no longer being maintained.

The county used an influx of state money to launch an aggressive mosquito control program, including the first aerial spraying in 20 years.

The efforts have continued this year. Although the virus has been detected in birds and mosquitoes, there have been no human cases of West Nile in Kern County in 2008.

So far, the state has reported a total of 355 cases, with the most -- 126 cases -- occurring in Los Angeles County.

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mary.engel@latimes.com