Health is something that one has to be very careful about traveling in this region. Some vaccinations and immunizations are mandatory and some are highly recommended. I checked with my local health center and got all the necessary shots, plus getting the proper anti malarial from the doctor ( I took Lariam), plus did some considerable reading, and checked the news regularly.

That being said, the people (travellers and residents) seem pretty much as healthy in Africa as anywhere else. Score card for 6 weeks for me and the people I travelled with:

1 bad chest cold (me) cured by a course of antibiotics.
1 eye infection (friend) cured with some chloramphenicol eye ointment I had handy.
1 infected toe (me) sorted out by cleaning with soap and water.
A bunch of infected feet (others on the overland trip), which got steadily worse for some people. Sandals and a humid climate seem tend to result in bangs and scrapes which rapidly get infected.
A bunch of upset stomaches (almost everyone at one point or another)
2 cases of malaria (overland trip)

Note: one of the people who got malaria was on nothing. It was quite scary the way the malaria came on but luckily we were in Nairobi by then and could get good medical care. Another lucky thing is it was not cerebral, but normal malaria. This isn't something to fool with.

  This book 'Bugs, Bites, and Bowels' by Dr Jane Wilson-Howarth I've found exceptionally good for advice on travelling related medical questions, and it is small enough to pack along. Becomes fascinating reading when you are sick in a strange country.