Travellers should get the latest medical advice on inoculations and malaria prevention at least three weeks prior to departure. A malaria risk exists all year round, but more around Mombasa and the lower coastal areas than in Nairobi and on the high central plateau. Immunisation against yellow fever, polio and typhoid are usually recommended. A yellow fever certificate is required by anyone arriving from an infected area. Other risks include diarrhoeal diseases. Protection against bites from sandflies, mosquitoes and tsetse flies is the best prevention against malaria and dengue fever, as well as other insect-borne diseases, including Rift Valley fever, sleeping sickness, leishmaniasis and Chikungunya fever. AIDS is a serious problem in Kenya and the necessary precautions should be taken. Water is of variable quality and visitors are advised to drink bottled water. Cholera outbreaks occur frequently, and travellers should take care not to drink contaminated water and be cautious of food prepared by unlicensed roadside vendors. There are good medical facilities in Nairobi and Mombasa but health insurance is essential