adjective
pestilent
PES-tuh-lunt/ˈpɛstələnt/
Causing or spreading serious disease.
The pestilent refuse attracts flies that carry contamination to the uncovered food.

Etymology
Latin pestilens meant “infected” or “unhealthy.” English extended this disease-related danger to things harmful to health or morals, giving the word a broader sense of deadly or damaging.
In context
gloomy lagoons stretched along its low coasts exhaling a pestilent odor while fever hovered over its sleepy Waters
More examples
- Workers wear protective gear while handling pestilent waste.
- The team tests the water for pestilent bacteria.
- The city works to control its pestilent rats.
Forms
pestilent
pestilence noun — A deadly epidemic or infectious disease.
Similar words
- pestilential
- Closely matches pestilent, especially for disease-ridden places or conditions.
- pathogenic
- Specifically describes organisms or substances capable of causing disease.
- infectious
- Emphasizes the ability to spread infection, rather than disease severity.