High Risk Areas for Malaria

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QUESTION:

Where are the high risk areas of malaria?

ANSWER:

Global malaria incidence rates (courtesy of the World Health Organisation)

Malaria is found in many tropical and sub-tropical parts of the world, although a few areas, through concerted control and prevention efforts, have eliminated the disease locally. Examples of this are the USA, most of the Mediterranean and parts of Central America. The highest burden of the disease is in Africa, although many parts of Asia, particularly India and south-east Asia, also suffer from a large number of cases every year. The map shows the risk of malaria around the world.

Introduction of malaria

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QUESTION:

What is the introduction of malaria?

ANSWER:

Malaria is introduced into the human host via mosquitoes, who pass the parasite into the human blood stream through their mouthparts as they take a blood meal. Since the development of both the mosquito and the parasite are temperature-dependent, and tend to favour warm, humid conditions (mosquito larvae require pools of still water to develop into adults), the distribution of malaria is limited to parts of the world where these temperature and humidity conditions are met.

However, cases of malaria can also be introduced into other parts of the world by travellers coming from malarial regions or by mosquitoes, already infected with malaria, being accidentally transported into non-malarial countries in aeroplanes or in ships. These kinds of introductions resulted in about 1500 cases of malaria reported in the United States in 2007, a country which is usually free of malarial transmission. These introductions are rare, and also short lived, as the conditions do not favour the continued survival of the transmission cycle. However, this is one of the worries regarding climate change; it may make some areas of the world, which currently do not have malaria, more climatically suited to transmission of the disease, thus allowing for introductions of the mosquitoes and the parasite in the future.