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Why can the El Tor biotype of Vibrio cholerae spread widely?

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Diagram of a water treatment plant showing the process from water inlet through mixing, coagulation, flocculation, settling, filtering, chemical treatment with chlorine, storage, and high-lift pumping to the distribution system. — water purification Water from inlets located in the water supply, such as a lake, is sent to be mixed, coagulated, and flocculated and is then sent to the waterworks for purification by filtering and chemical treatment. After being treated, the water is pumped into water mains for storage or distribution.

The El Tor biotype of Vibrio cholerae is responsible for the ongoing seventh pandemic due to two primary epidemiological characteristics that facilitate its wide transmission:1

Environmental Resilience: El Tor is a significantly hardier organism than the classical biotype, allowing it to survive for extended periods within aquatic environments.1
Asymptomatic Transmission: Many individuals infected with El Tor experience only mild symptoms or none at all. Because these individuals are more likely to travel than those who are severely ill, they play a critical role in spreading the bacterium across geographic regions.1

As an intestinal disease primarily spread via the fecal-oral route, cholera transmission is deeply linked to public health and the quality of water supplies. The ability of the El Tor biotype to persist in water and move through asymptomatic carriers underscores the vital importance of robust water purification and sanitation infrastructure in preventing the spread of waterborne illnesses.1