Bubonic plague constitutes about three-fourths of plague cases. Most characteristic is the early appearance of buboes, which are usually distributed in the groin and armpits. Septicemic plague may prove fatal before there is time for pneumonia to develop. If, however, pneumonia does occur, the patient becomes highly infectious. His contacts will contract pneumonic, not bubonic, plague.
Pneumonic plague is nearly always fatal.
In the 14th century, when this disease was known as the Black Death, some plague infections were bubonic and some were pneumonic. It has been calculated that one-fourth of the population of Europe, or 25,000,000 persons, died from plague during the great epidemic. The Great Plague of London in 1664-65 resulted in more than 70,000 deaths in a population estimated at 460,000. An outbreak in Canton and Hong Kong in 1894 left 80,000 to 100,000 dead, and within 20 years the disease spread from the southern Chinese ports throughout the whole world, resulting in more than 10,000,000 deaths. The rate of mortality from the Black Death varied from place to place.