The Flame Alphabet by Ben Marcus
The speech of children has mutated into a virus which is killing their parents. At first it only affects Jews, then everyone. Sam and Claire's lives are threatened when their daughter, Esther, becomes lethal. Each word she speaks is toxic to Sam and Claire. Radio transmissions from strange sources indicate that adults across the country are growing increasingly alarmed. All around, parents wither beneath the powerful screams of their children. Claire is already stricken and near death.
As the contagion spreads, Sam and Claire must leave Esther behind in order to survive. On fleeing, Sam finds himself in a government laboratory, where a group of scientists are conducting horrific tests, hoping to create non-lethal speech. What follows is a nightmarish vision of a world which is both completely alien and frighteningly familiar, as Sam presses on alone into a society whose boundaries are dissolving. Both morally engaged and wickedly entertaining, The Flame Alphabet asks the question: what is left of civilization when we lose the ability to communicate with those we love?