For unvaccinated individuals, antibiotics are given if the individual is exposed to Anthrax. Penicillin is the drug of choice. This form of plague is known a bubonic plague and still occurs in the world today, but less than twenty cases would typically be reported in the U.S. in one year. Bubonic plague is caused by the bacterium Yersinia pestis and is normally carried by rats and their fleas. It can be transmitted to humans by the bite of an infected flea.
Pneumonic plague is inhaled from infected cats.
For biological warfare it is expected that the attacker would try to induce pneumonic plague in humans by releasing a cloud of the same Yersinia pestis bacteria. Pneumonic plague transmitted in this way can be fatal in one to a few days if not treated immediately. After inhaling the plague organism there would be an incubation period of up to three days followed by a sudden onset of high fever and coughing up blood. Pneumonia would be evident on a chest x-ray. The pneumonia would progress rapidly producing inability to breath, failure of the circulatory system, and death in a few days.