Why people are worried about cholera during natural disasters.

Specifically, in the case of cholera, the breakdown of water/sanitation systems and significant decrease in hygeine standards can cause diarrheal diseases.

Crowding in shelters/camps, increasing contact between people

Mixing of different regional populations with different levels of vaccination or endemic disease

Contamination of drinking water

Spread of infectious mud or soils (leptospirosis)

Disruption or delay of vaccination programs

Death or disappearance of key medical and administrative staff

Destruction of key facilities (laboratories, hospitals, clinics, etc.)