Bioweapons

[Legbreaker]

We know (obviously) nukes were used in T2K and it's strongly implied chemical weapons too (Ruins of Warsaw, plus they're in the equipment lists), but how about bioweapons?
How widely do you think they were employed, how effective, who used them and just how persistent were the effects. Note we're talking a fictional reality here so IRL facts about their capabilities doesn't really have to come into this discussion.

If you've used them in game, what symptoms, etc did you apply?