Koch was appointed to lead a German Cholera Commission to Egypt during a cholera epidemic. This commission aimed to identify the cause of cholera and develop strategies for prevention and control.

In Egypt, Koch identified "Vibrio cholerae" as the causative agent of cholera. He isolated the comma-shaped bacterium from the intestines of cholera patients and demonstrated its presence in contaminated water sources. Although Filippo Pacini had described the bacterium earlier, Koch's work provided definitive proof of its role in causing the disease and developed improved methods for isolation and identification.

Koch traveled to India to further study cholera and confirm his findings. He conducted extensive research on cholera outbreaks in Calcutta and other regions, solidifying his understanding of the disease and its transmission.

Koch's work on cholera highlighted the importance of sanitation and water purification in preventing the spread of the disease. His research contributed to the development of improved sanitation practices and water treatment methods in many parts of the world. However, the complex epidemiology of Cholera and the role of asymptomatic carriers remained a source of disagreement between Koch and Max von Pettenkofer.