So I have been reading some Q/A here on gaming.stackexchange for dishonored and in the middle of it I thought to myself "Does shadow killing increase the amount of weepers, rats and overall plague in the city?" The reason I thought this is because if the dead bodies turn to ash then there is nothing for the rats to feast on and no disease to spread.
Side question: Does killing weepers decrease the amount of plague?
Best Answer
The amount of weepers and rats in the city is determined by your Chaos level.
Chaos level is determined by how many people you murder, and Shadow Kill is considered murder. So is killing weepers.
Thus, killing with Shadow Kill will increase the amount of plague-related stuff you encounter in the game, and can increase your chances of getting the "High Chaos" ending.