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Malaria is an infection of the blood that is carried from person to person by mosquitoes. The disease has been recognised for thousands of years and once was found almost everywhere except in the most northern areas of the world. Malaria has been wiped out in North America, Western Europe and Russia. However, it remains a serious problem in much of the tropical and subtropical world.

Millions of people continue to be infected every year and close to one million of them die. However, around 1,500 people a year are diagnosed with malaria in the UK after returning from abroad.

Malaria causes

Malaria is caused by protozoan of the genus Plasmodium.

  • Infection begins with a bite from an infected mosquito.
  • The parasite travels from the mosquito to your liver, where the parasite begins to reproduce.
  • The parasite leaves the liver and travels to the bloodstream, where it infects red blood cells. The parasite reproduces in the red blood cells, which destroys the cells and releases more parasites into the bloodstream.
  • If another mosquito bites an infected person, that mosquito can then carry the infection to someone else.
  • There are four species of Plasmodium that infect humans:
    • P vivax - Most common in India and Central and South America but found worldwide. It has an incubation period of 8-13 days. Infections can sometimes lead to life-threatening rupture of the spleen. In people treated only with chloroquine, this type of malaria can hide in the liver and return later.
    • P ovale - Rarely found outside Africa. This form of malaria has an incubation period of 8-17 days and can hide in the liver of partially treated people and return later.
    • P malariae - Found worldwide but less common than the other forms. This form of malaria has an incubation of 2-4 weeks. If untreated, the infection can last many years.
    • P falciparum - Common worldwide, this is the most life-threatening form of malaria. This parasite has an incubation period of 5-12 days. Resistance to many of the medicines used to treat or prevent malaria is increasing.
  • Although most people acquire malaria through mosquito bites, in some foreign countries the disease can have other sources.
    • Every year a handful of people are infected through blood transfusions or organ transplants.
    • IV drug users can develop malaria from sharing needles.
    • Each year a few babies are born to mothers who did not know they were infected. The babies then develop malaria.
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