Foreclosures Worsen Spread Of West Nile

The mortgage crisis has spread like a virus through the world's financial system - and may be spreading a real virus, too.

Soon after delinquent mortgages tripled in Kern County, Calif., cases of West Nile virus nearly tripled as well.

It was not coincidence, say William K. Reisen, PhD, of the Center for Vectorborne Diseases at the University of California, Davis, and colleagues.

"A dramatic increase in home foreclosures and abandoned homes [has] produced urban landscapes dotted with an expanded number of new mosquito habitats," they report. "These new larval habitats may have contributed to the unexpected early season increase in West Nile virus cases in Bakersfield during 2007."

It's an example of how events seemingly unrelated to disease can impact public health, says Roger Nasci, PhD, chief of the CDC's arboviral disease branch.

"This does emphasize that there are a number of complicating factors - which many people would not anticipate to be disease risks - that come into play," Nasci tells WebMD.

Could this happen elsewhere in the country? "It bears watching," says James Hughes, MD, associate director of the Southeastern Center for Emerging Biologic threats and professor of medicine and public health at Emory University. Hughes is the former head of the CDC's National Center for Infectious Diseases.

"This is a carefully done study that relates a rather dramatic increase in West Nile cases to changes in the environment in an urban setting," Hughes tells WebMD. "It illustrates how interplay between mosquitoes, birds, the environment, and a change in economic conditions affects disease."

Economic Crisis and West Nile

Reisen's team notes that it should not have been a good year for West Nile virus in the Bakersfield area. Winter and spring weather was exceptionally dry, reducing breeding opportunities for the mosquitoes that spread the bug from birds to humans.

The drought decreased bird populations in the spring, reducing breeding and increasing the percentage of birds already immune to West Nile virus.

Yet by June - a month earlier than in previous summers - populations of urban mosquito species skyrocketed. And given an ecological niche, house sparrow breeding soared, vastly increasing the number of birds able to carry the virus.

Sure enough, cases of West Nile virus rose sharply. What happened? The downturn in the housing market hit the Bakersfield area hard. There was an extraordinary increase in home foreclosures and abandoned homes.

Mosquito-control workers are trained to watch for neglected pools and spas. But they were frustrated by the six-foot-tall fences and locked gates that local laws required around outdoor pools.

Aerial photographs showed that 17% of pools and hot tubs in some neighborhoods had turned green with algae and were likely producing mosquitoes.

Although local authorities stepped up control efforts, the problem does not seem to be over. Reisen's team finds that this year, a rural species of mosquito - one much more likely to harbor West Nile virus - is taking over neglected pools.

And the mortgage crisis continues. Just last August, there were 303,879 foreclosure filings in the U.S. California's Kern County remains a foreclosure hotspot, but it isn't the only one.

The Reisen team's report appears ahead of print online in the November issue of the CDC journal Emerging Infectious Diseases.
By Daniel DeNoon
Reviewed by Louise Chang
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