I didn't expect this one but it makes sense. West Nile virus infections are up in California. The (possible) reason: unmaintained swimming pools, according to a paper in Emerging Infectious Diseases.
I saw this article in the proofs for Abstracts on Hygiene and Communicable Diseases, my abstract journal: "Delinquent Mortgages, Neglected Swimming Pools, and West Nile Virus, California".
The abstract says it all: "Adjustable rate mortgages and the downturn in the California housing market caused a 300% increase in notices of delinquency in Bakersfield, Kern County. This led to large numbers of neglected swimming pools, which were associated with a 276% increase in the number of human West Nile virus cases during the summer of 2007."
Actually unused swimming pools are a well known hazard for vector-borne diseases. Here are two more papers I found on Global Health:
Colonization of abandoned swimming pools by larval mosquitoes and their predators following Hurricane Katrina. Caillouët, K. A., Carlson, J. C. , Wesson, D. , Jordan, F. / Journal of Vector Ecology, 2008, Vol. 33, No. 1, pp. 166-172.
The role of unused swimming pools as a habitat for Anopheles immature stages in urban Malindi, Kenya. Impoinvil, D. E., Mbogo, C. M. , Keating, J. , Beier, J. C. / Journal of the American Mosquito Control Association, 2008, Vol. 24, No. 3, pp. 457-459
In fact I've just put myself off going swimming – a search on 'swimming pools' shows the hazards include waterborne diarrhoea (from various organisms), skin cancer (from the sun exposure), other cancers (from the chemicals), asthma (the chlorine), community acquired MRSA…
But remember the exercise is good for you.