plague

Plague is an infectious disease caused by the bacterium Yersinia pestis. It is a zoonosis that primarily cycles between wild rodents and fleas, but can also affect humans who become incidental hosts when exposed to infected fleas or to respiratory droplets from a person or animal with pneumonic plague.

Transmission occurs mainly through flea bites from infected rodents, though pneumonic plague can spread from person to person via respiratory droplets. Three clinical forms are recognized: bubonic, marked by swollen lymph nodes (buboes); septicemic, a systemic infection; and pneumonic, affecting the lungs. Symptoms vary by form but commonly include fever, weakness, and swollen nodes for bubonic plague; cough and chest pain for pneumonic plague; and signs of systemic infection for septicemic plague. Diagnosis relies on laboratory tests such as PCR or culture, with rapid identification critical for treatment.

Treatment requires prompt antibiotic therapy. Effective options include streptomycin, gentamicin, doxycycline, ciprofloxacin, or chloramphenicol, administered early. Without treatment, mortality is high, especially for pneumonic plague. Supportive care and infection control measures are important components of management.

Prevention focuses on reducing exposure to rodents and fleas, environmental sanitation, and, in some regions, vaccination for high-risk groups where available. Plague remains a notifiable disease in many countries. Historically significant pandemics include the Justinian plague and the Black Death; today, plague is enzootic in parts of Africa, Asia, and the Americas with periodic human cases, including occasional outbreaks in the western United States and other regions.