The fourth great pandemic invaded Europe by the usual routes and continued from 1863 to 1875. During its continuance there were two outbreaks in the U. S., one in 1867 and another in 1873.
That in 1873, when it was introduced into three widely separated parts of the country, was the last appearance of cholera in the U. S.
The fifth pandemic began in 1883 and affected particularly the Mediterranean seaports of France, Spain and Italy. It was during this epidemic, in 1883, that Koch, working in Egypt, discovered the cause of cholera, the Spirillum cholerae asiaticae.
A very serious outbreak of cholera, which originated in 1891, in pilgrims from the delta of the Ganges, reached Europe in 1892, almost a million deaths occurring in Russia. It was during this epidemic that cholera appeared in Hamburg and gave opportunity for those careful studies as to transmission of the disease to be later referred to.
It is usual to recognize a sixth pandemic which began in 1902 and spread over India, China and the Philippines. This pandemic continuing was a cause of great mortality among the soldiers of the recent Balkan war. During the World War there was much cholera among the Austrian forces in Galicia. It also prevailed in Bulgaria, Greece and Turkey.
Geographical Distribution.—Practically every pandemic when studied can be traced back to India and particularly to the delta of the Ganges, which may be considered the enduring focus of the disease.
Etiology and Epidemiology
Etiology.—The cholera vibrio, Spirillum cholerae asiaticae, was discovered by Koch in 1883 and is a short curved organism which, from its shape, is often called the comma bacillus. In addition to single spirilla there may be “S” shapes from attachment of pairs. In cultures in peptone solutions long filamentous forms may be seen which however are exceedingly rare in the rice-water stools. A stained smear from a fleck of mucus gives the fish-in-the-stream appearance. Besides comma-shaped organisms we may have coccoid or rod-shaped forms. In old cultures marked pleomorphism is often seen.
