Health in W Africa
If you travel for any length of time in West Africa you will probably get malaria, as well as a few other interesting diseases - random non malarial fevers are common, and stuff like conjunctivitis just sweeps through badly smashed up places and can't be avoided...
The good news is, that actually, as long as you are healthy and relatively fit, and prepared to have a few miserable nights, you won't have any serious problems... I worked in Sierra Leone & Liberia during the civil wars for various NGOs, and while I got both varieties of Malaria and a collection of other nasties, all of them clear up with self-treatment. The only colleague who died got Lassa Fever, a haemorragic fever which is endemic in Eastern SL and can be nasty, but he got it by walking round in sandals in a known rat infested area, with cuts on his feet... I went to fetch his colleague and clear out the house they'd been living in, and didn't feel at any risk, but I was wearing boots which I would always wear in W Africa, no matter how hot it is...
As for the Malaria - take treatment with you - I use Quinnine but for some it's a bit strong, Artesunate is a very good modern treatment (World Health Organisation recommend it - but buy it from a reputable supplier, the Chinese make it and they have been selling a lot of fake stuff...) and, most important for any fever, treat with LOADS of clean water. I'd personally say that the deaths from Malaria are almost entirely due to not drinking enough clean water when feverish - if you have to walk 1km down the hill to get to the pump and you have a high fever then you dehydrate instead, and then you die... I've had both Falciparum and Vivax Malaria many times and I know someone who had both together, but treatment, rest for a few days, and loads of water (think 6 litres a night when feverish) and you should be ok... Like so many tropical killers, Malaria is really fatal because of poverty - people who don't have clean water on tap and are already a bit weak.
The other thing is - make sure you have a GOOD first aid kit - I've had to use my own kit to have a sliced wrist sewn up (I could see right inside my arm until I went all faint at the sight of it!) after being chopped by a bit of corrugated iron roofing - even if you can find a clinic it probably won't have any supplies! And carry a sensible selection of antibiotics, they get sold by the colour of the pills rather than the function (really, I've had staff just go off to buy "the big red ones" because they had a bit of spare cash!) so it's fairly important to know what you have and what to use them for - bearing in mind that because of uncontrolled use most stuff is already antibiotic resistant!
And the last thought - wash your hands fairly obsessively! Carry the gel handwash - you'll find you use it a lot!
But - it's a great region (with the exception of Conakry airport - the worst and most corrupt place on earth!) and great fun - friendly people, weird stuff going on, and completely addictive!