Adjustable rate mortgages impact West Nile virus transmission

During 2007 the on-going West Nile virus epidemic in California was centered in Bakersfield at the southern end of the San Joaquin Valley. Severe drought conditions and high herd immunity within the peridomestic passerine community indicated a low risk for an outbreak. However, increases in adjustable rate mortgages and the down turn in the California housing market caused a 300% rise in notices of delinquency in Bakersfield, leading to large number of unmaintained swimming pools and a 276% rise in the number of human West Nile virus cases during the summer of 2007. These new peridomestic sources replaced surface pools as primary mosquito larval habitat and may have enabled the early season increase in mosquito infection incidence. Our study shows how anthropogenic sources may have enabled this outbreak of WNV and created new challenges for urban mosquito control.