It is recommended that before tourists come to Nairobi, that they should be vaccinated well in advance 6 weeks of their trip. The most common recommended vaccines for people traveling to Africa are Tetanus, Diphtheria, Polio, Typhoid, Hepatitis A, Hepatitis B, Yellow Fever, Rabies and Meningitis.
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There are very many internet cafés around Nairobi, but connection speeds and computers are not always super fast, but still you will manage to open your email, probably even use a webcam or watch YouTube. Prices are usually at ranges from 0.5KSh/minute to 1KSh/minute, usually with a minimum fee of 5-20KSh. The more expensive internet cafés are rarely better and the best ones charge 1KSh/minute with discounts for using the internet for longer. Most of the good cafés are found in Norwich Union which has quite a number just opposite Hilton Hotel next to Nandos while the expensive ones are found in malls in Westlands. Although it may be more appropriate for tourists to use the ones in Westlands since they are usually less crowded and are more exclusive but not necessarily faster or better in terms of equipment.
Free wireless internet is available at Java House restaurants and Doorman's coffee shops in the city and malls. Some bars like Havana in Westlands also offer free wifi. The internet cafe in Sarit Centre also has wireless internet available at a good speed and a reasonable price.
Mobile Phones are ubiquitous in Kenya with fairly good coverage from all providers Safaricom, Orange and Airtel that extends to most populated parts of the country. Safaricom has the best national coverage especially if you are using 3G data. The phone system is GSM 900 and 3G 2100 Asian and European standard. Phones and SIM cards are available at many locations throughout Nairobi and the country including at the airport. Phone prices are very competitive and priced for average income Kenyans. A basic phone may be obtained new from an independent dealer for ~2000/=. A vast majority of people use pre-paid phones with scratch-card top-ups available at a huge number of merchants across the country. All phones are sold "unlocked" for use on any network. Much business is conducted via mobile phone, so possession of one for even a relatively short stay in the country can be beneficial. Rates are extremely affordable with in-country calls at around 3/= per minute. Overseas calls cost around 5/= per minute to the United States ~USD$0.06/minute and 3/= per minute to India ~INR 1.80, USD 0.04 on the Airtel network.
3G data service is available in most coverage areas on Safaricom and is of a fairly high standard. The other networks have 3G in major population areas and EDGE/GPRS everywhere else. If you have a smart phone you should buy a data pack 200mb, 500mb or 1.5gb or your credit will go down very fast!
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Smoking is against the law out on the streets in the city center the downtown grid area with numerous skyscrapers. There are certain smoking zones, and outside of the city center it becomes much easier to find locations where it is acceptable. However, a general rule would be to not smoke along the side of any roads or streets with pedestrians and/or vehicles. Be observant and take your cues from other smokers - if there are no smokers or cigarette butts on the ground, it is likely a non-smoking location.
food and beverages
Be careful with the food that you eat outside the more upscale establishments. Before eating, make sure that the food is freshly and thoroughly cooked and served hot. Also avoid seafood,apart from the upmarket restaurants and hotels, and make sure that your fruits and vegetables have been properly sterilized in clean water. The safest fruits to eat are bananas and papayas. Do not drink tap water or brush your teeth with it. Only use bottled or canned drinks especially popular brands. Also, do not use ice as it may also be contaminated water, and remember that alcohol does not sterilize a drink. The general rule of thumb is, the more high end an establishment is, the greater the safety of the food and drink within.
insects
In Africa you are going to be exposed to yellow fever, dengue fever, other viral diseases, sleeping sickness, filariasis and malaria, although none of these diseases are a concern in Nairobi itself. When insects are biting you should cover up and wear long-sleeved shirts and trousers, socks and pyjamas especially when night falls. It is best to use an insect repellent that contains DEET on your exposed skin and clothing. As for mosquito nets, it is best to use a permethrin-impregnated net along with an insecticide such a pyrethrum coils or an electric mosquito killer during the night. And remember to spray your hotel room every evening.