Recent outbreaks of highly pathogenic avian influenza (also known as bird flu) have created a need for rapid and sensitive detection methods to mitigate its spread. Now, researchers have developed a prototype sensor that detects a type of influenza virus that causes bird flu (H5N1) in air samples. The low-cost handheld sensor detects the virus at levels below an infectious dose and could lead to rapid aerosol testing for airborne avian influenza.