Avian Flu, commonly called the Bird Flu, has been mentioned multiple times in "Mirror's Edge". According to news tickers from the lifts in several levels, Avian Flu has spread in the city.
Avian Flu is a real life disease that has raised fears of an epidemic or pandemic. Avian Flu refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. Speculation swirls around the disease; many believe that the highly censored and monitored nature of the news in the city may be used to scare civilians into believing that the flu is real as a background for nefarious activities.