What are the causes of cholera in modern age?

Same as always: The organism...Vibrio cholera, usually serotype o1, spread thru contaminated water.

Contamination & poor: sanitation. " Infection due to V. cholerae begins with the ingestion of contaminated water or food. After passage through the acid barrier of the stomach, the organism colonizes the epithelium of the small intestine ." REF: http://www.who.int/water_sanitation_health/dwq/admicrob6.pdf