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Malaria is an infectious disease caused by Plasmodium parasites. The are spread by the bite of infected female Anopheles mosquitos. There are five types of Plasmodium (P) species which infect humans; P. malariae, P. falciparum, P. vivax, P. ovale and P. knowlesi.
Very rarely, transmission can also occur through infection, blood transfusion and sharing of needles or syringes.
When a human is bitten by an infected mosquito the parasites enter the blood stream and travel to the liver. After infection there is usually an incubation period of 7-30 days, after which the parasites enter red blood cells and develop. Some people don’t develop symptoms for several months, particularly if they took inadequate doses of anti-malarial medication. P. vivax and P. ovale cause relapsing disease as the parasite can stay dormant in the liver, before re-entering the blood stream months, and even years, after the initial infection. Infection by P. falciparum can cause life-threatening disease, as can P knowlesi.
The World Health Organisation declared Australia malaria-free in 1981, however several hundred cases are diagnosed in Australia each year. These people generally contract the disease while travelling, most commonly in Papua New Guinea. There were also seven cases of locally acquired malaria in the Torres Strait in 2010-11.
Ninety percent of all malaria deaths occur in sub-Saharan Africa. Malaria also exists in regions of Central and South America, parts of the Caribbean, Africa, Asia (including South Asia, Southeast Asia, and the Middle East), Eastern Europe and the South Pacific.
Worldwide, the World Health Organisation estimated there were 212 million new cases of malaria and 429,000 deaths (down 30% from 2012) in 2015.
Last Review Date: April 28, 2023
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