Chronic wasting disease (CWD) is a transmissible, neurodegenerative disorder in deer that causes inability to eat, stumbling, drooling, and lack of fear of humans, and in all cases is ultimately fatal. "You can have deer that are infected live for two or more years, and it can take a very long time before they show clinical signs of it," says Michelle Gibison, diagnostic laboratory testing manager at the University of Pennsylvania School of Veterinary Medicine's Wildlife Futures Program. That means they can infect other deer in that time.