Defense Imagery photograph by Pfc. Crystal Madriz, we see U.S. soldiers dressed in protective gear, dragging a simulated casualty from a rubble pile during a joint training exercise by the Air Force and Army involving biological and chemical warfare response, casualty rescue, and decontamination at Fort Pickett, Va., in 2008.
Numerous countries around the world keep stockpiles of biological weapons and creating bioterrorism weapons is relatively easy. Fortunately there have been only two successful bioterror attacks, with others thwarted in the planning stages. The United States suffered both attacks--the mysterious anthrax letters in 2001 and the attack by followers of Bhagwan Shree Rajneesh, who in 1984 tried to rig elections in The Dalles, Oregon, by putting salmonella in the salad bars of ten local restaurants. The letters killed five people but the Rajneesh attack luckily resulted in no fatalities.
Despite the rarity of bioterror attacks, they remain a real threat and national governments spend a large amount of money preparing for them. If there's ever another global war, that training will probably come in handy. In any post-apocalyptic scenario, the survivors will have dealt with such plagues and would either been immune or have developed immunity. There are always mutated strains, however. . .