plagues

A plague is an infectious disease or widespread calamity, historically associated with Yersinia pestis, a bacterium that causes bubonic, septicemic, and pneumonic forms. While the term often refers to deadly urban outbreaks, it can also describe any severe epidemic described as a plague.

Transmission occurs primarily via flea bites from infected rodents, with the pneumonic form spread person-to-person through respiratory droplets. Septicemic plague can result from bacteremia without overt buboes. Other organisms are sometimes described as causing "plagues" in looser usage, but Y. pestis is the classic agent.

Symptoms vary by form: bubonic plague features swollen lymph nodes (buboes), fever, weakness; pneumonic plague involves coughing, chest pain, and rapid breathing; septicemic plague causes abdominal pain, shock.

Historically, plagues have shaped societies: the Justinian Plague (6th c.), the Black Death in the 14th century, and the Third Pandemic beginning in the 19th century. Large outbreaks prompted public health responses such as quarantine, travel restrictions, sanitary improvements, and rodent/flea control. The term also appears in descriptions of localized outbreaks like the Great Plague of London.

In modern times, plague remains rare but endemic in parts of Africa, the Americas, and Asia. Treatment with antibiotics is effective if begun early; preventive measures include surveillance, rodent control, and prompt isolation of cases. The term "plague" also serves as a metaphor for any devastating epidemic.