V. cholerae’s primary reservoir is an aquatic environment, where
it exists in a free-living state associated with phytoplankton, zooplankton,
algae, or copepods (12, 13). Transmission into a host’s
gastrointestinal system occurs by ingestion of contaminated food
or water. Bacteria surviving the acidity of the stomach colonize the
small intestine and cause increased intestinal secretions, leading to
large volumes of watery diarrhea (14). V. cholerae exits the human
body during such diarrheal purges, allowing disease transmission
or seeding an environmental reservoir.