This document highlights the history and characteristics of plague.
Plague is a zoonotic infection caused by the Gram-negative bacillus Yersinia pestis, which has been the cause of three great human pandemics responsible for more deaths than any other infectious agent in history. The naturally occurring disease in humans is transmitted from rodents and is characterized by the abrupt onset of high fever, painful swelling of the lymph nodes, and bacteremia. The disease is acquired from animal fleas, contact with infected animals, and rarely, from other humans, via aerosol or direct contact with infected secretions. Medical officers must understand the typical way in which humans contract plague in nature to be able to differentiate endemic disease from plague used in biological warfare. First, a die-off of animals that harbor bacteria-infected fleas will occur. Second, troops who have been in close proximity to such infected mammals will become infected. In the most likely biological warfare scenario, plague would be spread via aerosol. This would be followed by a rapid person-to-person spread of fulminant pneumonia, characterized by blood-tinged sputum. If an enemy force were to release fleas infected with Y pestis, then soldiers would present with classic bubonic plague before a die-off of animals occurred. The most common form of plague is bubonic plague, characterized by painful lymphadenopathy and severe symptoms of fever, chills, and headache. Septicemic plague without localized lymphadenopathy occurs less commonly and is difficult to diagnose. Secondary pneumonia may follow either the bubonic or the septicemic form. Primary pneumonic plague is spread by airborne transmission, when aerosols from an infected human or animal are inhaled. Diagnosis is established by isolating the organism from blood or other tissues. Patients should be isolated and treated with aminoglycosides, preferably streptomycin, plus chloramphenicol when meningitis is suspected or shock is present. A licensed, killed, whole-cell vaccine is available to protect humans against bubonic, but not against primary pneumonic, plague. 75 references