Malaria is a highly infectious disease spread primarily through mosquitoes. The five strains of malaria are caused by an infection by Plasmodium parasites, which are most commonly transmitted through the bite of the Anopheles mosquito. Given the nature of its transmission, several factors affect the spread of malaria. These include climate, geographical location, and environmental conditions. Malaria's spread is also affected by the availability of vaccines and infectious disease control.
The main determinant of the spread of malaria is the disease's prevalence in a given area. Mosquitoes will often bite infected individuals, taking in the parasites along with the victim's blood. The parasites, the most dangerous among which is Plasmodium falciparum, then develop within the mosquito and find their way into their host's saliva. The next time the infected mosquito bites a person, it will transmit the parasites in its saliva, resulting in a new infection. This creates a persistent cycle in malaria-prone areas.
The disease is endemic in several locations across the globe. Countries along the equator are at higher risk for malaria, with sub-Saharan Africa being the most infected region. Roughly 90 percent of the world's malaria-related casualties occurs in this area, a significant number given that the World Health Organization estimates that the disease causes nearly 1 million annual deaths. Other areas at risk for malaria include South America and equatorial regions of Asia. Frequent travel to these areas greatly increases an individual's risk of being infected with the condition, which boosts the risk of spreading the disease elsewhere.
Climate plays a major role in the spread of malaria, as certain weather conditions allow for increased reproduction rates in mosquitoes. Warm areas with occasional to moderate rainfall tend to harbor more mosquitoes than drier areas, as the insects lay their eggs in stagnant waters. Countries that experience monsoon rains may also see mosquito population growth in between wet seasons, when accumulated rainfall is allowed to sit still over an extended period of time.
The spread of malaria is also greater in areas where disease control methods are not readily available. These methods include mosquito nets, vaccines, and insect repellents. Educational material, such as guides on keeping homes mosquito-free, is another major factor in preventing malaria. Areas where medication and education on how malaria spreads are unavailable suffer higher infection rates, which lends to the disease's persistence.
