Cuba is a safe destination for travellers. The diseases and distractions are few and usually, you can just go about the business of enjoying the beach and the bonhomie without spending your energies on health and wealth issues. Crime is of the petty kind and the few bugs that there are are easily avoidable with a little savvy and caution.
Yellow fever certificates are required only if you are travelling from an infected area, cholera certificates are not required. There is some prevalence of polio, typhoid and malaria so you may consider inoculation against the first two and a prophylactic for the last. Incidents of Hepatitis A and dengue have been reported, as has rabies. Human fascioliasis is endemic to the entire central American region so think twice before drinking untreated water and keep away from raw vegetables and fruits that may have been washed in untreated water. These diseases are not restricted to outlying areas so these precautions are relevant even in Havana.
Water from the main water supply is treated and safe. Steer clear of tap water outside Havana; bottled water is readily available all over Cuba.
Common crimes that travellers should be wary of are pick pocketing, mugging and thievery of unattended luggage. Be alert in crowded streets, markets and buses, don’t wander into secluded areas particularly after dark, and make sure you don’t leave your valuables unattended; burglaries have been reported from some budget hotels where thieves have climbed in through windows.
Medical facilities in Cuba are quite good. Foreigners must pay for services so do take out a medical insurance policy before travelling to Cuba.