How thermal-imaging cameras can spot flu fevers

The swiftly spreading Influenza A H1N1 virus has the world taking emergency measures to prevent transmission as far as possible, thermal- imaging cameras are being used to screen passengers at airports but how do they work?

In the wake of the Influenza virus and earlier during the SARS outbreak thermal imaging cameras have been rolled out in airports to screen passengers for the fever. An AP report states that these cameras are just like ordinary cameras but instead of recording light that objects reflect, they respond to heat and work even in the dark. AP: "Recordings from these cameras show up on video screens with hotter objects looking brighter. The systems are very sensitive, measuring temperatures down to a fraction of a degree Fahrenheit, said Andrew Sarangan, an associate professor in the University of Dayton's electro-optics program." The transportation secretary, Juan Molinar said that Mexico already has 10 such cameras and 40 more are being brought in for the eight largest airports in the country. Though the cameras can detect higher temperatures they cannot possibly diagnose the flu, and passengers may have a higher body temperature for various reasons. Hence further testing must be implemented once passengers are found with higher temperatures. The Irisys' cameras cost about $3000 and work by merging visual and thermal images to create a "heat picture" of the passenger.This image shows up on the screen behind the camera just like a regular digital camera and a pointer automatically shows the hottest area in the picture. Tony Trunzo, senior vice president at Wilsonville, Ore-based Flir systems Inc says Flir's cameras have improved since the Sars outbreak. He concludes that it is best to screen one person at a time for clarity.