Malaria epidemiology and demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-in-Chief: Rim Halaby, M.D. [3]

Overview

Worldwide, 3.4 billion people live in areas at risk of malaria transmission in 106 countries and territories. The World Health Organization estimates that in 2012 malaria caused 207 million clinical episodes, and 627,000 deaths. An estimated 91% of deaths in 2010 occurred in the African Region. The vast majority of cases of malaria occur in children under the age of 5 years. Malaria is presently endemic in a broad band around the equator, in areas of the Americas, many parts of Asia, and much of Africa; however, it is in sub-Saharan Africa where 85– 90% of malaria fatalities occur. Malaria is present depending primarily on climatic factors such as temperature, humidity, and rainfall.

Epidemiology and Demographics

P. vivax is the most common cause of infection, responsible for about 80 % of all malaria cases. However, P. falciparum is the most important cause of disease, and responsible for about 15% of infections and 90% of deaths.[1]

Incidence

  • The World Health Organization estimates that in 2012 malaria caused 207 million clinical episodes worldwide.[2]
  • In the United States, approximately 1,500–2,000 cases of malaria are reported every year, almost all in recent travelers. Reported malaria cases reached a 40-year high of 1,925 in 2011.[2]

Age

The vast majority of cases of malaria occurs in children under the age of 5 years.[3]

Mortality

  • The World Health Organization estimates that in 2012 malaria caused 207 million clinical episodes, and 627,000 deaths. An estimated 91% of deaths in 2010 were in the African Region.[2]

Geographic Distribution

  • Malaria is presently endemic in a broad band around the equator, in areas of the Americas, many parts of Asia, and much of Africa; however, it is in sub-Saharan Africa where 85– 90% of malaria fatalities occur.[4]
  • The geographic distribution of malaria within large regions is complex, and malarial and malaria-free areas are often found close to each other.[5]
  • Shown below is an image depicting an approximation of the parts of the world where malaria transmission occurs (source: CDC).



Rural Areas vs Cities

  • Malaria is more common in rural areas than in cities; this contrasts with dengue fever, where urban areas present the greater risk.[7]
  • The cities of the Vietnam, Laos and Cambodia are essentially malaria-free, but the disease is present in many rural regions.[8]
  • In Africa malaria is present in both rural and urban areas, though the risk is lower in the larger cities.[9]

Climatic Factors

  • Malaria is found mainly on climatic factors such as temperature, humidity, and rainfall.
  • 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.
  • In many malaria-endemic countries, malaria transmission does not occur in all parts of the country. Even within tropical and subtropical areas, transmission will not occur:
    • At very high altitudes
    • During colder seasons in some areas
    • In deserts (excluding the oases)
    • In some countries where transmission has been interrupted through successful control/elimination programs.
  • Generally, in warmer regions closer to the equator transmission will be more intense and malaria is transmitted year-round. The highest transmission is found in Africa South of the Sahara and in parts of Oceania such as Papua New Guinea.
  • In cooler regions, transmission will be less intense and more seasonal. There, P. vivax might be more prevalent because it tolerates better lower temperatures.
  • Many temperate areas, such as western Europe and the United States, economic development and public health measures have succeeded in eliminating malaria. However, most of these areas have Anopheles mosquitoes that can transmit malaria, and the reintroduction of the disease is a constant risk.
  • In drier areas, outbreaks of malaria can be predicted with reasonable accuracy by mapping rainfall.[10]

Socio-Economic Effects

  • Malaria is not just a disease commonly associated with poverty, but is also a cause of poverty and a major hindrance to economic development.
  • The disease has been associated with major negative economic effects on regions where it is widespread.
  • A comparison of average per capita GDP in 1995, adjusted to give parity of purchasing power, between malarious and non-malarious countries demonstrates a fivefold difference (US$1,526 versus US$8,268).
  • In countries where malaria is common, average per capita GDP has risen (between 1965 and 1990) only 0.4% per year, compared to 2.4% per year in other countries.[11]
  • Correlation does not imply causation, and the prevalence is at least partly because these regions do not have the financial capacities to prevent malaria. In its entirety, the economic impact of malaria has been estimated to cost Africa US$12 billion every year.
  • The economic impact includes costs of health care, working days lost due to sickness, days lost in education, decreased productivity due to brain damage from cerebral malaria, and loss of investment and tourism.[3]
  • In some countries with a heavy malaria burden, the disease may account for as much as 40% of public health expenditure, 30-50% of inpatient admissions, and up to 50% of outpatient visits.[12]

References

  1. Mendis K, Sina B, Marchesini P, Carter R (2001). "The neglected burden of Plasmodium vivax malaria" (PDF). Am J Trop Med Hyg. 64 (1-2 Suppl): 97–106. PMID 11425182.
  2. 2.0 2.1 2.2 Malaria Facts. CDC.gov accessed on 07/24/2014 [1]
  3. 3.0 3.1 Greenwood BM, Bojang K, Whitty CJ, Targett GA (2005). "Malaria". Lancet. 365: 1487–1498. PMID 15850634.
  4. Layne SP. "Principles of Infectious Disease Epidemiology /" (PDF). EPI 220. UCLA Department of Epidemiology. Retrieved 2007-06-15.
  5. Greenwood B, Mutabingwa T (2002). "Malaria in 2002". Nature. 415: 670–2. PMID 11832954.
  6. "Centers for Disease Control and Prevention (CDC)".
  7. Van Benthem B, Vanwambeke S, Khantikul N, Burghoorn-Maas C, Panart K, Oskam L, Lambin E, Somboon P (2005). "Spatial patterns of and risk factors for seropositivity for dengue infection". Am J Trop Med Hyg. 72 (2): 201–8. PMID 15741558.
  8. Trung H, Van Bortel W, Sochantha T, Keokenchanh K, Quang N, Cong L, Coosemans M (2004). "Malaria transmission and major malaria vectors in different geographical areas of Southeast Asia". Trop Med Int Health. 9 (2): 230–7. PMID 15040560.
  9. Keiser J, Utzinger J, Caldas de Castro M, Smith T, Tanner M, Singer B (2004). "Urbanization in sub-saharan Africa and implication for malaria control". Am J Trop Med Hyg. 71 (2 Suppl): 118–27. PMID 15331827.
  10. Grover-Kopec E, Kawano M, Klaver R, Blumenthal B, Ceccato P, Connor S (2005). "An online operational rainfall-monitoring resource for epidemic malaria early warning systems in Africa". Malar J. 4: 6. PMID 15663795.
  11. Sachs J, Malaney P (2002). "The economic and social burden of malaria". Nature. 415: 680–5. PMID 11832956.
  12. Roll Back Malaria. "Economic costs of malaria". WHO. Retrieved 2006-09-21.



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