MIASMA

[noun]

1. noxious exhalations from putrescent organic matter; poisonous effluvia or germs polluting the atmosphere.

2. a dangerous, foreboding, or deathlike influence or atmosphere.

Etymology: from New Latin < Greek míasma, “stain, pollution”, akin to miaínein, “to pollute, stain”.

[Billy Norrby - Fog]