Cholera (1817 - 1823)

The first cholera pandemic began in Jessore, India, and spread through most of the region and then to neighboring areas. It was the first of 7 major cholera pandemics that have killed millions of people. A British physician named John Snow knew some things about how to prevent it from spreading, and in 1854 stemmed the outbreak by isolating its source to a particular water pump in London's Soho neighborhood.

The World Health Organization has called cholera "the forgotten pandemic" and said that its seventh outbreak, which began in 1961, continues to this day. Cholera reportedly infects 1.3 million to 4 million people every year, with annual fatalities ranging from 21,000 to 143,000.

As cholera is caused by ingesting food or water contaminated with a certain bacteria, it overwhelmingly harms countries hampered by extreme wealth inequality and lack of social development. Cholera continues to change the world by hurting the parts of it least able to defend themselves, while richer countries barely worry about it.