If AIDS mutates and becomes airborne, that would also be threatening. Ditto for hantavirus, hepatitis and millions of other diseases. Heck, imagine if black wid

If AIDS mutates and becomes airborne, that would also be threatening. Ditto for hantavirus, hepatitis and millions of other diseases. Heck, imagine if black widow venom become airborne and victims started producing more airborne venom themselves! If you're willing to dip into the pool of things that are vanishingly unlikely, there are lots of extremely bad things that could happen.