Nightshade

Most humans in Nightshade have had their curiosity disabled. The Cheshires have contaminated water supply with what would best be described as 'nanobots' - but is usually called “curiosity toxin” by survivors that don't exactly have the means to verify how the substance functions, assuming for a moment that they have a theory about the absent emotion at all (and have correctly identified the absent emotion, even, as it's not something frequently amiss).