That year, the British physician John Snow, who was working in a poor area of London, identified contaminated water as the means of transmission of the disease.

To test his theory, he convinced officials to remove the pump handle, and the number of cholera cases in the area immediately declined.

Cholera hit Ireland in 1849 and killed many of the Irish Famine survivors, already weakened by starvation and fever.

[16] In Siam, cholera outbreak which started from Penang before passing to Pattani, Songkla, Samut Prakarn, Bangkok, Pathum Thani, Phitsanuloke and Ang Sila from June to July 1849 had killed at least 5,457 people in Bangkok and the estimated number of death from cholera outbreak varied from 15000 to 40000 people.

In 1859, an outbreak in Bengal contributed to transmission of the disease by travelers and troops to Iran, Iraq, Arabia and Russia.

Some United States scientists began to believe that cholera was somehow associated with African Americans, as the disease was prevalent in the South in areas of black populations.

Current researchers note their populations were underserved in terms of sanitation infrastructure, and health care, and they lived near the waterways by which travelers and ships carried the disease.

[28] The events surrounding the cholera pandemic in Bologna in 1855 were described by the city's Sanitation Department or Delegation, published in 1857.

This outbreak, which killed 616 people, is best known for the physician John Snow's study of its causes and his hypothesis that germ-contaminated water was the source of cholera, rather than particles in the air (referred to as "miasma").

Although his studies were not entirely conclusive, his advocacy convinced the local council to disable the Broad Street pump by removing its handle.

This discovery came to influence public health and the construction of improved sanitation facilities beginning in the mid-19th century.