In We Happy Few, the plague is an infection that can be given to the player if they are attacked by a plagued wastrel. The plague will continue to make the player more and more tired before it kills them. The amount of time it takes to kill the player varies, but players can't sleep it off and it doesn't go away until the player dies. Nevertheless, according to the official Compulsion website, since the Life in Technicolour Update, plague "will no longer kill you. Just game things."
Cure for the plague
The plague can be cured with a phenocycline syringe. A syringe and its recipe can both be found at the Lud's Holm Bridge at the entrance to the second Garden District island. It is recommended to always have a phenocyline syringe on hand at all times.