There has been an ongoing outbreak of Cholera in Cuba since July of last year. The 12 cases reported since July 2013 were from people who had travelled to Havana. The 2 food service centers linked to these outbreaks have since adopted up to date sanitary measures.
Travellers are advised to use caution when travelling abroad. All water should be boiled or treated with chlorine. Bottled water with unbroken seals and canned/bottled carbonated beverages are safe to drink. Safe drinking water should be used at all times to brush teeth and to wash and prepare food (including ice). Make sure food preparation areas are cleaned with soap and safe water and allowed to dry before use.
For further information on Safe food and water practices please see: http://novatravelclinic.com/travel-health/food-and-water-safety/
There is a vaccine for protection against travelers diarrhea and cholera: http://novatravelclinic.com/vaccinations/travellers-diarrhea/. Ensure you seek travel health advice prior to your departure to ensure all your vaccines are up to date.