It is well-known that US culture is a dominant force and a world-wide phenomenon. But it is possible that its most troubling export has yet to be accounted for? America has been the world leader in generating new mental health treatments and modern theories: it exports psychopharmaceuticals and categorises disorders, thereby defining mental illness and health. The outcome of these efforts is just now coming to light: it turns out that the US has not only been changing the way the world talks about and treats mental illness -- it has been changing the mental illnesses themselves. Watters travels from China to Tanzania to bring home the unsettling conclusion that the virus is the US: as Americanized ways of treating mental illnesses are introduced, they are is fact spreading the diseases and shaping, if not creating, the mental illnesses of our time.