Back in 2009, the global H1N1 (swine flu) outbreak was the cause of a lot of concern. But while many public health officials were focused on the flu itself, a team of neuroscientists led by researchers at Stanford University noticed something strange: That year saw a huge uptick in the number of people diagnosed with narcolepsy, a sleep disorder famous for causing its sufferers to be rendered unconscious for several minutes during unpredictable "sleep attacks." They suspected that the flu vaccines, which were being deployed in high numbers worldwide, might have had something to do with it. People vaccinated with one in particular, called Pandemrix, showed particularly high levels, and the researchers sought to figure out why. Their study, published today in Science Translational Medicine, could shed new light on what causes narcolepsy, which is still poorly understood.