Swampaire's Croup

Lasting for at least five days, the means by which Swampaire's Croup is transmitted is not clear, but they seem to have something to do with the catching and preparing of snails (superstitious peasants ascribe this to the vengeance of snails that were not caught or gutted cleanly). Sufferers develop a loud and barking cough, often accompanied by the expectoration of lurid green phlegm. This green substance sweats from the pores in the disease's later stages, giving the victim an oily, greenish sheen that has sometimes led to sufferers being mistaken for Undead.

Source
pg. 26
 * Warhammer Fantasy RPG 2nd ED -- Barony of the Damned