In southern Ontario, West Nile virus trackers with the Hastings and Prince Edward counties\u2019 health unit have more than 373,000 square miles to cover. Their job: look for dead birds that might harbor the potentially fatal mosquito-born disease and check standing water for mosquitoes and larvae. Then warn the public about where the virus has been detected and urge people to take precautions, such as wearing pants and long sleeves and using insect repellent.Since April, the 17 inspectors of the West Nile virus surveillance program have been collecting data (date, time, GPS coordinates for field sites, information about birds, mosquitoes and larvae) using a PDA application designed for the task. The application, Assur H&S (health and safety), is from Calgary, Alberta-based vendor Carmina Technologies, which specializes in pest control and disease monitoring systems. It is designed for PDAs and has been easy for county inspectors to use, says Glen Hudgin, the agency\u2019s director of public health inspection. Users synchronize the PDAs with computers at the office to analyze data collected.Standalone software applications for PDAs "are fantastic. With an application like this, I imagine you could train somebody in an hour or less," says David Shiple, a Forrester Research analyst.West Nile threatens much of North America until the first hard frost occurs (usually October in Ontario). As of Aug. 28, Canada confirmed nine West Nile cases, while the United States reported 1,482 human cases in 34 states, with 24 deaths. Hudgin says the proactive approach helps contain the West Nile risk. "We\u2019re quite confident that the work we\u2019re doing [in the field] is helping to reduce the risk to the public," Hudgin says.