What is the most deadly and horrible disease that you have found?

Question: What is the most deadly and horrible disease that you have found?
- Keywords:
  deadly,
  disease,
  horrible
Asked by Nelly to Sophie on 10 Nov 2016.
- Sophie Nedelec answered on 10 Nov 2016:
  
  I recently found out about parasitic wasps who lay their eggs inside aphids, the wasp larvae develop inside the aphid’s body eating it alive until it turns into a mummy! My friend is working on those guys in a greenhouse where I work at the moment.

Question: What is the most deadly and horrible disease that you have found?