Plague is an infectious disease of animals and humans caused by the bacterium Yersinia pestis. Y. pestis is found in rodents and their fleas in many areas around the world.

Pneumonic plague occurs when Y. pestis infects the lungs. The first signs of illness in pneumonic plague are fever, headache, weakness, and cough productive of bloody or watery sputum. The pneumonia progresses over 2 to 4 days and may cause septic shock and, without early treatment, death.

Person-to-person transmission of pneumonic plague occurs through respiratory droplets, which can only infect those who have face-to-face contact with the ill patient.

Early treatment of pneumonic plague is essential. Several antibiotics are effective, including streptomycin, tetracycline, and chloramphenicol.

There is no vaccine against plague.

Prophylactic antibiotic treatment for seven days will protect persons who have had face-to-face contact with infected patients.