Bubonic plague

Bubonic plague, disease transmitted to humans by fleas from infected rats. One form of the plague called Black Death swept through Europe and parts of Asia in the 1300s, killing three-quarters of the population in 20 years. Symptoms include fever, chills, and enlarged, painful lymph nodes (buboes), particularly in the groin. In its black form, hemorrhages turn black. The antibiotics tetracycline and streptomycin as well as rat control and sanitation have greatly reduced the mortality rate.

See also: Epidemic.