Cholera is an infection in the small intestine caused by the bacterium Vibrio cholerae. The main symptoms are watery diarrhea and vomiting. Transmission occurs primarily by drinking water or eating food that has been contaminated by the feces (waste product) of an infected person, including one with no apparent symptoms. The severity of the diarrhea and vomiting can lead to rapid dehydration and electrolyte imbalance, and death in some cases. The primary treatment is oral rehydration therapy, typically with oral rehydration solution, to replace water and electrolytes. If this is not tolerated or does not provide improvement fast enough, intravenous fluids can also be used. Antibacterial drugs are beneficial in those with severe disease to shorten its duration and severity. Worldwide, it affects 3–5 million people and causes 100,000–130,000 deaths a year as of 2010. Cholera was one of the earliest infections to be studied by epidemiological methods.
U.S. POWs on Hawaii were starved by their Japanese captors and came down with nutrition deficiency diseases like Beriberi. The Japanese didn't care since they were not contagious but they were panicked by an outbreak of cholera since it killed several guards too.
Unit 731 experimented with a number of infectious diseases to develop biological weapons including cholera. This proved effective and a delivery system was developed involving porcelain bomb casings filled with cholera bacilli. These were shipped to Unit 113 for use in Yunnan Province, in China. The forces of Chiang Kai-Shek were still fighting the Japanese Army and received some supplies from the British in India but the outbreak of disease disrupted this.