Plague

The plague is caused by a bacterium known as Yersinia pestis, which primarily infects rodents and their fleas, but which may be transmitted to humans by the bite of rodent fleas, typically when rodents die off. The disease may also be transmitted by inhalation of infected droplets, which may be coughed into the air by a person with plague pneumonia, or by direct exposure to infected blood or tissues.
The plague occurs in several forms. Bubonic plague, historically the most common, is characterized by fever, chills, muscle aches, and malaise, associated with the development of an acutely swollen, exquisitely painful lymph node, known as a bubo, near the site of the flea bite. Buboes occur most often in the groin, since fleas usually bite the legs, followed in frequency by the neck and armpit. Septicemic plague is an overwhelming bloodstream infection resulting in fever, obtundation, dangerously low pressure, bleeding abnormalities, and kidney failure. Plague pneumonia results from inhalation of infected droplets or bloodstream spread of the organism to the lungs. Initial symptoms include rapid onset of fever, chills, headache, body aches, weakness, dizziness, and chest discomfort, followed by cough, increasing chest pain, and difficulty breathing. The sputum is often bloody. Severe cases are complicated by respiratory failure, circulatory collapse, and death.
Most travelers are at extremely low risk for the plague, even when the disease is known to be present in the animal population. Those who may have contact with rodents or their fleas should bring along a bottle of doxycycline, to be taken prophylactically if exposure occurs. Those less than eight years of age or allergic to doxycycline may take trimethoprim-sulfamethoxazole instead. To minimize risk, travelers should avoid areas containing rodent burrows or nests, never handle sick or dead animals, use appropriate insecticides for any pets, and follow insect protection measures, as described elsewhere. The manufacture of plague vaccine, which was effective against bubonic but not pneumonic plague, was discontinued in 1999.
From the World Health Organization (WHO)
Plague fact sheet
Geographic distribution of the plague (map)
Human plague in 1997 (PDF). Weekly Epidemiological Record, Vol. 74, 41, 1999.
Human plague in 1998 and 1999(PDF). Weekly Epidemiological Record, Vol. 75, 42, 2000.
Plague manual
From the Centers for Disease Control (CDC)
Plague
Plague Home Page
Plague General Information
Plague Fact Sheet
Questions and Answers about Plague
Plague: Natural History
Plague: Diagnosis
Plague Information
Prevention of Plague: Recommendations of the Advisory Committee on Immunization Practices (PDF) (comprehensive review; primarily for physicians)
From the U.K. Health Protection Agency
Plague - general information
Interim Guidelines for Action in the Event of a Deliberate Release (PDF)
Clinical pictures - plague
From the Journal of the American Medical Association
Plague as a Biological Weapon
From the United States Department of Defense

Medical Aspects of Chemical and Biological Warfare (PDF)