Foreclosures Worsen Spread of West Nile
Neglected Pools in Foreclosed Homes Breeding Mosquitoes With West Nile Virus
Oct. 2, 2008 -- 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
It was not coincidence, say William K. Reisen, PhD, of the Center for
Vectorborne Diseases at the University of California, Davis, and
"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
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
"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
"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
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
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
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
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.