Malaria is endemic to a wide stretch around the equator that covers South and Central America, Africa, the Middle East and South-East Asia. A disease is endemic when it occurs routinely in an area. An epidemic, on the other hand, is a temporary explosion of cases of a disease in an area.
Numbers of people surpassing 100,000,000 are newly infected yearly, with hundreds of thousands dying as a result. There are three conditions conductive to malaria being endemic, and that determine which efforts to curb the disease are most likely to bear fruit in a particular region:
1. High human density
2. High anopheles mosquito density
3. High rates of transmission from mosquitoes to humans and from humans to mosquitoes (as you remember, the gametophytes of the Plasmodium parasite fuse inside the mosquito to create sporozoites; these are transmitted to humans and undergo further development to produce gametophytes again, which get transmitted back to mosquitoes)
Malaria is transmitted via a vector which carries it without being affected, before passing it onto the final host of the parasite. In this case it is carried by the mosquito which transfers it via its bite in saliva.
Symptoms upon infection include fever, headache, vomiting and fatigue.
The reproductive cells of the parasite (gametocytes) fuse inside the mosquito which then delivers the sporozoites into the host via the bite. The Plasmodium falciparum sporozoites get taken up by the lymphatic system in a human, and later they pass through the liver where they asexually reproduce, and then travel to red blood cells before releasing their gametocytes again.
Their reproduction in the liver doesn’t bring any symptoms, but once they invade red blood cells and destroy them to invade more red blood cells, fever occurs in waves as new parasites move from the liver cells into red blood cells.
Red blood cells can become sticky due to so-called adhesion knobs on their surface. The parasite can easily hide inside the red blood cells to evade the host’s immune system, as well as in the liver.
Economically speaking, it may be more worthwhile to prevent the disease than to treat it. This is feasible in areas like China where the money needed by the affected Chinese provinces to execute this is a small percentage of the healthcare budget, but not necessarily in other parts of the world affected by malaria, such as Tanzania, where these measures would by comparison be equivalent to a large portion of the budget (a fifth).
Social and enconomic infrastructures determine the outcome of infection, as treatment with antimalarials depends on the progression of the disease and the state of the patient. A vaccine is not in use yet, but trials are undergoing for a vaccine that could confer tolerance to the parasite (as opposed to immunity).
Under complete medical supervision and early treatment of an infected individual in the UK (acquired from an endemic region, as Plasmodium is not present in Europe; it can’t reproduce in the anopheles mosquito below 20 degrees Celsius), recovery is virtually guaranteed. Travellers can start treatment prior to travel or infection as a means of prevention, and use mosquito repelling substances. Both these approaches might not be available or practical to someone living in an endemic area, and within an area there might be people of different socio-economic status with different options or none at all regarding treatment and prevention.
Mass efforts to address this include low cost measures such as nets repelling to mosquitoes, and awareness of the symptoms of the disease and its transmission. Female mosquitoes bite at dusk and at night, and covering skin can minimise the risk of getting bitten.