Empty homes with stagnant swimming pools have Palm Beach County health officials worried that the wave of foreclosures has created breeding reservoirs for disease-carrying mosquitoes. Cleanup efforts are slow, and detection of problems is hard to accomplish, the county health department says. More than 4,200 foreclosure notices have been filed against Palm Beach County homeowners since June 15, according to realquest.com. It’s unclear how many of those homes have swimming pools. The county’s mosquito control division used a helicopter to spray about 215,000 acres between Military Trail and the Glades for mosquitoes Wednesday night.