I have had malaria twice. Once I came fairly close to dying, but the second time it merely killed certain holiday plans and gave me something to talk about. I have a couple of notes to add to what Kentfallen, Motoedde and Docsherlock describes above:
Immunity, which is characteristic of almost everyone who grows up (and survives infancy and early childhood) in malarial zones, is both partial and temporary; that is, locals have a degree of resistance which protects them to some degree, but this goes away in the absence of exposure to the parasite.
Because resistance to the parasite is partial, a great many of the locals you see around you in sub-Saharan Africa are suffering from clinical or subclinical infection with attendant anemia, liver dysfunction, etc. This is worth keeping in mind if tempted to complain about the listlessness of local workers.
Because resistance is temporary, it is not uncommon for formerly-resistant Africans who have been away for a time to return (for a holiday visit, for example) and promptly contract malaria. As a Westerner who last contracted malaria several years ago, I can be assumed to have absolutely no immunity.
Resistance is to some degree genetic. Africans tend to have it; Britons (and others of European extraction) tend to not have it. The gene which confers resistance is the same one which makes you susceptible to sickle cell anemia, so there is a sort of delicate balance involved between one deadly illness and the other. You can easily research the connection if you are interested.
You can contract malaria from just a single mosquito bite. On the other hand, you may get bitten by a lot of mosquitoes and never get the disease.
The mosquitoes which carry malaria tend to feed at dusk and dawn, and tend to attack at floor level. If you’ve ever had the experience of sitting around a table drinking
or eating dinner in West Africa while mosquitoes swarmed around your bare ankles, biting like crazy, you’ll remember it.
There are other reasons to try not to get bitten by mosquitoes, including the possibility of dengue fever, which is incurable by Western medicine and is reportedly very uncomfortable in addition to sometimes fatal.
You can contract malaria while taking anti-malarials. I’ve done this twice.
Many pharmaceutical drugs available in Africa are partially or fully fake, or outdated, or have been improperly stored. I have had personal experience with this, and it has convinced me that I am better off buying medications at inflated prices in my home country, rather than risking my safety in order to save a few bucks. YMMV.
Much of what has been written, especially on-line, about anti-malarial medications is overblown and needlessly alarmist. However, it is certainly true that some people react badly to, especially, mefloquine. On the other hand, doxycycline tends to give you ferocious sunburns, and chloroquine tends to be pretty ineffective in many areas. Malarone has worked well for me; its main side effect is to empty my bank account rapidly!
It is worth remembering that much of all the rest of what you read on-line about malaria is at least equally inaccurate. I like the WHO and CDC websites, personally.
Arteminisin is the basis for all those “Arte….” medications, in Africa as elsewhere. It is based on an Asian herbal remedy, and it is the best preventative and curative available today. However, it is often adulterated or counterfeited. Furthermore, it is supposed to be taken in combination with at least one other anti-malarial, not alone. This is done in order to prevent a situation in which the plasmodium parasite rapidly develops resistance to the drug (which is actually the only effective treatment remaining in certain areas of SE Asia). This is easily researched elsewhere.
Two of the four varieties of malaria parasite can hide in the liver, leading to repeated phases of acute malaria even after you take a “cure.” Therefore, it is crucial to know the specific strain and/or take an automatic course of yet another anti-malarial, primaquine, which attacks the parasite in its liver stage. There are medical implications involved in taking primaquine (involving an incompatible blood factor carried by some people) which you can research yourself.
Whatever else you may conclude about your own risk tolerance, malaria is not a joke. I ran a temperature of 106 (F) my first time around and was fortunate to be rescued by friends. This is easily high enough to cause permanent brain damage (debatable, in my case!) or death.
Finally, remember that YMMV….with potentially life-threatening consequences. In making these sorts of decisions, we are altering the margins of safety within which we all live our lives. It is probably best that we exercise a degree of caution when doing so.