German microbiologist Robert Koch isolated Vibrio cholerae and proposed postulates to explain how bacteria caused disease.

[8] (See: Scientific advances) In 1881, the cholera bacterium spread both East and West, and eventually reached Europe and Latin America.

[2][9] From its endemic origin in the Ganges Delta in West Bengal, there was a virulent outbreak in the Punjab and Lahore in northwest India in the years 1881–82, with a very serious death rate.

[14] Quarantine measures for ships and immigrants based on the findings of the British physician, John Snow, prevented cholera outbreaks in Great Britain and the United States.

[17] The disease continued westward in 1892, across the Punjab (with 75,000 cholera deaths), and raged on through Afghanistan and claimed 60,000 lives in Persia,[17][18] and then reached Imperial Russia which suffered a staggering morbidity rate, exacerbated by the Russian famine of 1891–1892.

Brazil was hit with cholera in 1893–95, mainly along the railway in the Paraíba Valley, through ships carrying immigrants from Europe,[23][24][25] Argentina in 1894–95, and Uruguay in 1895.

[2] In late June 1883, the first cases of cholera in Egypt, recently occupied by the British Empire in 1882, occurred in the port city of Damietta on the Mediterranean coast and rapidly spread in the Nile Delta and throughout the country in the summer and autumn,[26] "notwithstanding cordons maintained with a degree of severity and cruelty almost unexampled".

[29] The main source of the outbreak were East European Jews, mainly from Imperial Russia, that were on their way to cross the Atlantic Ocean, trying to escape the appalling conditions, the 1891–1892 famine and cholera epidemic, and antisemitic restrictions (such as the expulsion of Jews from Moscow early in 1892) in their home country.

[21] Before they boarded, the emigrants were housed in special barracks, jointly financed by the city and the Hamburg America Line shipping company, that were built in the harbour.

Conditions were often inadequate and communal latrines discharged their untreated excrement directly into the Elbe river flowing through the city.

[29][30] Although at the time it was fiercely contested, the infection of the city's water-supply was the main reason for the rapid spread of the cholera.

[29][31] In 1893 violent riots broke out, because the public objected to sanitary officers trying to enforce regulations for the prevention of spread of the disease.

Twain criticizes how impoverished individuals were forcefully moved to pest houses where many perished unrecognized and unceremoniously buried.

Koch helped establish that the disease was more specifically contagious and was transmitted by exposure to the feces of an infected person, including through contaminated water supply.

The germ theory of cholera introduced new methods of protection against the disease, such as the use of chemical disinfectants and heat to kill the bacillus (by boiling water, for instance).

[28] Waldemar Haffkine, a Russian-French bacteriologist, focused his research on developing a cholera vaccine, and produced an attenuated form of the bacterium.

To definitively test the vaccine, he needed an area where cholera was common to conduct large trials on humans and moved to India in 1894.

After Haffkine's experiments in Calcutta showed promising results, he was asked by the owners of tea plantations in Assam to vaccinate their workers.