Malaria epidemiology and demographics: Difference between revisions
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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.<ref>{{cite web | author = Layne SP | title = Principles of Infectious Disease Epidemiology /| work = EPI 220 | publisher = UCLA Department of Epidemiology | url = http://web.archive.org/web/20060220083223/http://www.ph.ucla.edu/epi/layne/Epidemiology+220/07.malaria.pdf | accessdate = 2007-06-15}}</ref> The geographic distribution of malaria within large regions is complex, and malarial and malaria-free areas are often found close to each other.<ref name="greenwood2002">{{cite journal | author=Greenwood B, Mutabingwa T | title=Malaria in 2002 | journal=Nature | year=2002 | volume=415 | pages=670–2 | pmid = 11832954}}</ref> | 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.<ref>{{cite web | author = Layne SP | title = Principles of Infectious Disease Epidemiology /| work = EPI 220 | publisher = UCLA Department of Epidemiology | url = http://web.archive.org/web/20060220083223/http://www.ph.ucla.edu/epi/layne/Epidemiology+220/07.malaria.pdf | accessdate = 2007-06-15}}</ref> The geographic distribution of malaria within large regions is complex, and malarial and malaria-free areas are often found close to each other.<ref name="greenwood2002">{{cite journal | author=Greenwood B, Mutabingwa T | title=Malaria in 2002 | journal=Nature | year=2002 | volume=415 | pages=670–2 | pmid = 11832954}}</ref> | ||
Shown below is an image depicting an approximation of the parts of the world where malaria transmission occurs (source: CDC). | |||
[[File:Geographical distribution of malaria.jpg]] | |||
====Rural Areas vs Cities==== | ====Rural Areas vs Cities==== | ||
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In 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 reintroduction of the disease is a constant risk. | In 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 reintroduction of the disease is a constant risk. | ||
In drier areas, outbreaks of malaria can be predicted with reasonable accuracy by mapping rainfall.<ref>{{cite journal | author = Grover-Kopec E, Kawano M, Klaver R, Blumenthal B, Ceccato P, Connor S | title = An online operational rainfall-monitoring resource for epidemic malaria early warning systems in Africa. | url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15663795 | journal = Malar J | volume = 4 | issue = | pages = 6 | year = 2005 | pmid = 15663795}}</ref> | |||
===Socio-Economic Effects=== | ===Socio-Economic Effects=== | ||
Revision as of 19:07, 24 July 2014
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Malaria epidemiology and demographics On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
It is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Each year, it causes disease in approximately 650 million people and kills between one and three million, most of them young children in Sub-Saharan Africa.
Epidemiology and Demographics
Distribution and Impact
Malaria causes about 400–900 million cases of fever and approximately one to three million deaths annually [1] — this represents at least one death every 30 seconds. The vast majority of cases occur in children under the age of 5 years;[2] pregnant women are also especially vulnerable. Despite efforts to reduce transmission and increase treatment, there has been little change in which areas are at risk of this disease since 1992.[3] Indeed, if the prevalence of malaria stays on its present upwards course, the death rate could double in the next twenty years.[1] Precise statistics are unknown because many cases occur in rural areas where people do not have access to hospitals or the means to afford health care. Consequently, the majority of cases are undocumented.[1]
Although co-infection with HIV and malaria does cause increased mortality, this is less of a problem than with HIV/tuberculosis co-infection, due to the two diseases usually attacking different age-ranges, with malaria being most common in the young and active tuberculosis most common in the old.[4] Although HIV/malaria co-infection produces less severe symptoms than the interaction between HIV and TB, HIV and malaria do contribute to each other's spread. This effect comes from malaria increasing viral load and HIV infection increasing a person's susceptibility to malaria infection.[5]
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.[6] The geographic distribution of malaria within large regions is complex, and malarial and malaria-free areas are often found close to each other.[7]
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 is in contrast to dengue fever where urban areas present the greater risk.[8] For example, the cities of the Vietnam, Laos and Cambodia are essentially malaria-free, but the disease is present in many rural regions.[9]
By contrast, in Africa malaria is present in both rural and urban areas, though the risk is lower in the larger cities.[10]
Climatic Factors
Where malaria is found depends 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 is more tolerant of lower ambient temperatures.
In 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 reintroduction of the disease is a constant risk.
In drier areas, outbreaks of malaria can be predicted with reasonable accuracy by mapping rainfall.[11]
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). Moreover, 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.[12] However, 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.[2] 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.[13]
References
- ↑ 1.0 1.1 1.2 Breman J (2001). "The ears of the hippopotamus: manifestations, determinants, and estimates of the malaria burden". Am J Trop Med Hyg. 64 (1-2 Suppl): 1–11. PMID 11425172.
- ↑ 2.0 2.1 Greenwood BM, Bojang K, Whitty CJ, Targett GA (2005). "Malaria". Lancet. 365: 1487–1498. PMID 15850634.
- ↑ Hay S, Guerra C, Tatem A, Noor A, Snow R (2004). "The global distribution and population at risk of malaria: past, present, and future". Lancet Infect Dis. 4 (6): 327–36. PMID 15172341.
- ↑ Korenromp E, Williams B, de Vlas S, Gouws E, Gilks C, Ghys P, Nahlen B (2005). "Malaria attributable to the HIV-1 epidemic, sub-Saharan Africa". Emerg Infect Dis. 11 (9): 1410–9. PMID 16229771.
- ↑ Abu-Raddad L, Patnaik P, Kublin J (2006). "Dual infection with HIV and malaria fuels the spread of both diseases in sub-Saharan Africa". Science. 314 (5805): 1603–6. PMID 17158329.
- ↑ Layne SP. "Principles of Infectious Disease Epidemiology /" (PDF). EPI 220. UCLA Department of Epidemiology. Retrieved 2007-06-15.
- ↑ Greenwood B, Mutabingwa T (2002). "Malaria in 2002". Nature. 415: 670–2. PMID 11832954.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Sachs J, Malaney P (2002). "The economic and social burden of malaria". Nature. 415: 680–5. PMID 11832956.
- ↑ Roll Back Malaria. "Economic costs of malaria". WHO. Retrieved 2006-09-21.