At most properties, and in most areas, the water is safe to drink, and is less chemically treated that you might imagine. In those rare cases where a property itself is concerned about water, bottled water is always provided. Indeed, bottled water is readily available at properties, and on safari.
Malaria is a prevalent disease in much of Africa, but lodges all take precautions - with a combination of mosquito nets, and sprays. Be sure to continue the prophylactic regime when you return home, as it is generally required up to 4 weeks after travel as well. Please see Malaria information for more details.
Yellow Fever is caused by a virus carried by a species of mosquito, and has been known to occur in certain East African countries. There have been no recent outbreaks, but as yellow fever is contagious, many countries require travellers to get a yellow fever inoculation. Travellers should be inoculated at least 10 days prior to travel (a certificate is issued).
The inoculation certificate is not generally required when entering the country in question (e.g. Kenya or Tanzania), but is required for your return to your country of residence. Please consult your Travel Clinic, or doctor, prior to travel.
Bilharzia (Schistosomiasis) is a waterborne parasite carried by snails, and occurs in stagnant water of lakes, dams and slow flowing rivers. However, lodges, and guides, will always caution you as to where it is safe to swim. In Africa, many lakes and rivers are home to Hippopotamus and Crocodiles anyway - so swimming is not generally recommended!
If you travel extensively in remote areas, you might also want to consult your Travel Clinic about Hepatitis A and B, and tetanus inoculations.
When on Safari, always ensure that you drink sufficient quantities of water. Day time temperatures can be extreme, even in winter, and you don't want to suffer from dehydration.
Complications from sunburn should also not be ignored - always wear a hat with a brim, and ensure that you carry a good supply of protection cream.