Areas Where Malaria Occurs

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QUESTION

Can you please tell me the high, low and no risk areas for malaria.

ANSWER

Malaria requires certain climatic conditions, both for its own development as well as for the survival of its vector mosquitoes. As such, malaria transmission is concentrated in lowland areas of the tropics, where there is sufficient freshwater for mosquito breeding. However, malaria can also seasonably be transmitted in areas away from the tropics. Similarly, some tropical and sub-tropical areas have implemented successful control programs which has significantly reduced or even eliminated transmission.

Currently, high risk areas for malaria transmission include most of sub-Saharan Africa (except for the highlands of Ethiopia, Tanzania, Kenya and Eritrea – areas over 1800 meters of altitude tend to have less malaria), most of northern South America (except areas over 2000m, and many urban cities are also free of malaria), parts of Central America, some Caribbean islands, India, south-east Asia (again, apart from highland areas) and Oceania. Low risk areas include parts of southern Africa (i.e. northern South Africa), parts of Central America (including most of Mexico, though some parts of the south may be considered higher risk), parts of the Middle East and parts of China. There is no known malaria in North America, Europe, most of North Africa, Australia, New Zealand, Japan, the eastern coastal regions of Brazil, most of southern South America and northern Asia. For a detailed and up to date map of malaria risk around the world, please see the Malaria Map

Distribution of Malaria

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QUESTION

Where does malaria mostly take place?

ANSWER

Malaria is mainly transmitted in tropical regions of the world; while some transmission does occur outside of the tropics, it tends to be seasonal in these areas (i.e. usually only during periods of high temperature/high rainfall). Within the tropics, malaria is found on all continents, though the highest number of cases is in Africa, which is also where over 90% of deaths due to malaria occur (of these, most are children under the age of 5). Outside Africa, the next highest levels of malaria are in India and south-east Asia and the western Pacific (such as Papua New Guinea).

Geographic Range of Malaria

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QUESTION

Has the geographic range of malaria increased over the past 20 – 30 years? I have read that preventative measures have helped lower rates of infection, but I’m interested in the extension of the range itself.

ANSWER

That is a very interesting question, and one that garners quite a lot of debate. Preventative measures have actually also helped to limit the range of malaria globally. For example, malaria used to be relatively common in the Mediterranean basin and south-eastern United States, but control measures (mainly based around killing mosquitoes and removing suitable mosquito habitat) has largely eradicated malaria from these areas.

However, there is concern that on-going and future climate change has and will change the  distribution of malaria globally. For example, some predictions have suggested that malaria might be able to re-establish itself in the Mediterranean and Middle East, due to higher rainfall and higher winter minimums of temperature. Additionally, malaria may be able to spread to higher altitudes in areas where it is already present at low elevations. This is of huge concern in places like Kenya: Nairobi, the capital city (with around 5million people), sits at 1660 m altitude, and as such currently has generally negligible levels of malaria transmission. However, if climate change enables malaria to move up to this altitude, a huge number of people will be at additional risk of infection. Worryingly, there is some evidence from the Kenyan highlands that these changes are already underway.

Having said this, there are also parts of the world which might see malaria transmission ease as a result of climate change. This is particularly the case where rainfall is expected to decrease, or change significantly in relation to temperature. Moreover, some scientists think that on-going control efforts, particularly with respect to the distribution of bednets, vector control and greater coverage of diagnosis and treatment will continue to reduce the geographical spread of malaria over and beyond the changes associated with climate change. These scientists have compiled a map of Plasmodium falciparum transmission now as compared to data from before control interventions were rolled out—the reduction of transmission risk in many parts of the world, are clear to see (see below).

changing plasmodium falciparum map

Maps showing changes in transmission risk and endemicity of Plasmodium falciparum malaria between approximately 1900 (a) and now (b). (c) shows the balance of change in malaria transmission between the two time periods: the higher the negative number, the greater the reduction in malaria transmission. A positive number indicates increased malaria transmission. The different classes of malaria transmission risk are as follows: hypoendemic, prevalence < 10%; mesoendemic, PR ≥ 10% and < 50%; hyperendemic, prevalence ≥ 50% and < 75%; holoendemic, prevalence ≥ 75%. Image reproduced here from Gething et al., (2010), 'Climate change and the global malaria recession', in Nature, volume 465, pages 342-345.

What countries have malaria?

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QUESTION

In which countries can it be found?

ANSWER

Malaria is found in many parts of Africa, Latin America, Asia, and Oceania. The exact distribution depends on climatic variables (namely heat and sufficient rainfall, for the development of the mosquitoes which transmit malaria) and also how successful a particular country or region has been at controlling malaria.

For example, malaria was once found in parts of the U.S. and Europe, but successful campaigns to control mosquitoes and treat cases led to elimination of transmission. The same is true in other parts of the world; for example, in Malaysia, transmission is successfully controlled in Kuala Lumpur, but malaria can still be found in many parts of the surrounding countryside.

Please visit the CDC website for an interactive map of malaria distribution around the world.

Malaria Distribution

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QUESTION

What countries have malaria?

ANSWER

Prior to the advent of modern methods for controlling malaria, it was present on every continent in the whole except Antarctica. The transmission of malaria depends on an appropriate climate, both for the development of the parasite and the mosquitoes that it requires as a vector. This limits malaria to areas that are sufficiently warm and with sufficient rainfall to provide pools of stagnant water for the development of mosquito larvae.

In practice, this means that malaria can be transmitted year round in the tropics (apart from areas of high altitude and deserts), most of the year in the sub-tropics (predominantly during rainy periods) and even seasonally in temperate latitudes (during the warmer months). As a result, malaria has historically been present in the United States and even in England, at a latitude of over 50 degrees north.

However, modern control measures, such as insecticide spraying and epidemiological surveillance, has greatly reduced transmission of malaria in many parts of the world, and especially in temperate regions where the force of infection was already lower than elsewhere in the world. As such, nowadays malaria is confined to tropical and sub-tropical Central and South America, certain Caribbean islands (such as Haiti), sub-Saharan Africa (apart from most of Namibia and South Africa), parts of the Middle East, the Indian sub-continent, south-east Asia (excluding major cities such as Singapore) and many of the Indo-Pacific islands (including Papua New Guinea). Of these, by far the largest number of deaths from malaria occur in sub-Saharan Africa.

See the CDC’s interactive map of malaria distribution for more information.

Malaria in Africa

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QUESTION

What percent of Africa has malaria?

ANSWER

That is very difficult to measure, but maps of malaria transmission potential show that malaria is potentially present across most of the continent, excluding the heart of the Sahara and Kalahari deserts, and the highlands of Ethiopia, Lesotho and Uganda/Rwanda. Other parts of the continent, such as the coastline of North Africa (along the Mediterranean) and much of South Africa and Zimbabwe likely only experiences seasonal transmission of malaria, with some parts of the year too cold and/or dry to support transmission. The below map shows the distribution of malaria throughout Africa, and should give you some idea of the percentage landcover that is affected.

Distribution of endemic malaria

Distribution of endemic malaria in Africa. Picture courtesy of http://siteresources.worldbank.org/NEWS/Images/malaria-map.jpg

Where is Malaria Found?

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QUESTION

Where is malaria found?

ANSWER

Malaria is found throughout the world’s tropical and sub-tropical areas, and mainly in Central and South America, Africa, Asia and the Indo-Pacific region. It is most common in tropical regions, where transmission occurs year-round; in sub-tropical and temperate areas, transmission may only occur during seasons that have appropriate climatic conditions. This includes sufficiently high temperature and water availability for the growth and development of the mosquito, which transmits the disease. The map below shows the estimated risk for malaria across the world, courtesy of the World Health Organisation.

To search an up-to-date malaria map by country, please visit the CDC Malaria Map application.

global malaria risk

Map of estimated malaria risk (2010 data). Courtesy of WHO (http://www.who.int/en/)

In What Countries is Malaria Found?

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QUESTION

What countries can malaria be found in?

ANSWER

Malaria is found on every continent of the world except Antartica—however, regular transmission every year mainly only occurs in Central and South America, Africa, parts of the Middle East, Asia and parts of Oceania/the Pacific Islands.

The world’s highest areas of malaria prevalence and transmission occur in sub-Saharan Africa, followed by India, south-east Asia (especially the Indo-Pacific islands, such as Papua New Guinea) and parts of Central America and northern South America.

Based on the latest available data, the top five countries reporting the most annual malaria deaths were Kenya, the Democratic Republic of Congo, Cote d’Ivoire and Burkina Faso. However, the top five countries with the highest number of malaria cases per 100,000 members of the population were Guinea, Botswana, Burundi, Zambia and Malawi.

The Solomon Islands have the highest number of malaria cases per 100,000 outside of Africa, followed by Yemen. Note that these statistics are highly dependent on quality of diagnosis, treatment and reporting!

Malaria as a Global Issue

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QUESTION

How is malaria a global issue?

ANSWER

Malaria is a global issue because it is found all over the world, with people in 109 countries at everyday risk of infection and approximately 250 million cases every year. In fact, every year, cases of malaria are reported from every continent of the world apart from Antartica; moreover, there are concerns that in the face of climate change, more areas of the world will become suitable for transmission of malaria, making it even more widespread.

Malaria Locations in Africa

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QUESTION:

Where in Africa is malaria mainly found?

ANSWER:

The distribution of malaria is constrained by two main factors: temperature and the presence of suitable mosquito hosts. These mosquitoes also depend on certain climatic conditions for their development, namely warm temperatures and sufficient rainfall to produce stagnant water, required by mosquito larvae. As such, although most of Africa lies within latitudes that would normally produce warm enough temperatures for at least seasonal transmission of malaria, in fact the disease is not found everywhere.

spatial distribution Plasmodium falciparum malaria Africa
Spatial distribution of Plasmodium falciparum malaria in Africa. From Hay et al., 2009, “A world malaria map: Plasmodium falciparum endemicity in 2007”, PLoS Medicine 6(3)

Winters in the Mediterranean region and most of the Cape are too cold for malaria, and in these areas, control interventions have largely eliminated the risk of summer sporadic transmission. Similarly, at high elevations, temperatures are too low for the development of the parasite and/or the mosquito vector. For this reason, places such as central Zimbabwe, the high plateau of Ethiopia and even large cities like Nairobi are relatively malaria-free. Finally, the Sahara and Kalahari desert regions are too dry – there is insufficient moisture for the survival of the mosquito vectors.

Based on these factors, the hotspots for malaria transmission in Africa lie in lowland areas with moderate to high rainfall. The map above shows the distribution of Plasmodium falciparum, the most severe and deadly form of the disease.