Malaria: An Epidemiological Overview Distribution: Environmental risk factors

Because of malaria's mode of transmission (through Anopheles mosquito bites), it is an almost exclusively tropical disease. "Temperature is particularly critical. For example, at temperatures below 20°C (68°F), Plasmodium falciparum (which causes severe malaria) cannot complete its growth cycle in the Anopheles mosquito, and thus cannot be transmitted" ("Where malaria occurs," 2010). But where the parasites can complete their growth cycle, wherever the Anopheles mosquitoes can survive and multiply, so do incidents of the disease. Prevalence and intensity is highest where the mosquito can breed year 'round in regions nearest the equator -- particularly in sub-Saharan Africa ("Where malaria occurs," 2010). In some tropical and subtropical countries, prevalence has been reduced because the disease cannot be transmitted at higher altitudes, during colder seasons, in deserts (mosquitos prefer humid climates), and also because of government mosquito control programs ("Where malaria occurs," 2010).

Distribution: Social factors

The fact that control programs have significantly reduced or eliminated the prevalence of malaria in many tropical and subtropical regions highlights the fact that environmental conditions alone cannot explain the prevalence of outbreaks. In the southern United States, for example, malaria used to be a threat until a public health campaign designed to eliminate the disease through appropriate control measures was successful. With the creation of the U.S. Tennessee Valley Authority (TVA) during the New Deal, however, a program for controlling malaria in the region was established. From a disease that affected 30% of the population when the TVA was incorporated in 1933, thanks to control operations by 1947 the disease was eliminated...

"Mosquito breeding sites were reduced by controlling water levels and insecticide applications" ("The history of malaria," 2010). As a result of this success, the National Malaria Eradication Program was established in 1947. "By the end of 1949, over 4,650,000 housespray applications had been made. In 1947, 15,000 malaria cases were reported. By 1950, only 2,000 cases were reported. By 1951, malaria was considered eliminated from the United States" ("The history of malaria," 2010).
Unfortunately, in sub-Saharan Africa, the healthcare infrastructure is not stable enough to support such efforts. Poverty and a lack of organizational resources mean that the types of effective antimalarial campaigns which were so successful in the U.S. And Europe cannot be established. Even simple and inexpensive measures such as providing mosquito nets to residents have proven to be challenging to implement. The World Health Organization (WHO) recommends a three-pronged strategy for malaria reduction in affected areas: environmental management; biological and chemical controls; and personal prevention strategies. Environmental management includes drainage (eliminating the breeding-grounds of mosquitos); biological and chemical controls include insect sprays, larvicides, or introducing fish which eat mosquito larvae; and personal protective strategies include personal use of insecticides and nets. "IVM supports more accessible and affordable disease diagnosis and treatment with effective anti-malarial drugs, within the framework of a multi-disease control approach" ("Malaria control," 2015).

Distribution: Malaria and genetics

"It is now clear that malaria parasites have imposed strong selective forces on the human genome in endemic regions" (Driss et al. 2011).Certain genetic factors can make individuals more or less susceptible to malaria. For…