Use of oral cholera vaccine as a vaccine probe to define the geographical dimensions of person-to-person transmission of cholera.

•Cholera, a waterborne disease, is known to be transmitted from person to person.•However, the geographical dimensions of this transmission are uncertain.•Oral cholera vaccines were used as probes to define these dimensions.•Dimensions were 500m in rural Bangladesh and 150m in Kolkata, India.•Person-to-person transmission of cholera can be sustained over long distances.