While malaria is not commonly seen by physicians in the western world, there are still 200 million cases of malaria annually, leading to about 445 000 deaths a year. Many of these are children. So, with global travel, it is still important for clinicians worldwide to be able to readily identify and treat this deadly disease.
Where is malaria found?
The distribution patterns of malaria have changed over the past few centuries. In the 19th century, it was present in much of Europe, North America, and parts of Australia. Today, malaria is confined to more tropical climates like Mexico, South and Central America, the Indian subcontinent, and Southeast Asia. But 90% of malaria cases occur in sub-Saharan Africa.
What causes malaria?
Malaria results from infection with one of various species of the parasite Plasmodium. There are five main types of malaria—with varying disease severity and global distribution—that you should be familiar with.
- Plasmodium falciparum
- Plasmodium vivax
- Plasmodium knowlesi
- Plasmodium ovale
- Plasmodium malariae
1. Plasmodium falciparum
Most cases of malaria in sub-Saharan Africa—about 190 million cases per year—are caused by Plasmodium falciparum, the deadliest form of malaria.
2. Plasmodium vivax
Plasmodium vivax is the next most common form. It is globally distributed, but only accounts for 8.5 million cases each year.
3. Plasmodium knowlesi
Plasmodium knowlesi is found in Southeast Asia, Malaysia, and Borneo. Given this limited geographic distribution, it’s the rarest form of malaria in humans.
4. Plasmodium ovale
Plasmodium ovale has a worldwide distribution but is not very common overall.
5. Plasmodium malariae
Similar to Plasmodium ovale, Plasmodium malariae has a worldwide distribution, but is also not very common.
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- Ashley, EA, Phyo, AP, and Woodrow, CJ. 2018. Malaria. Lancet. 391:1608–1621. PMID: 29631781
- Fairhurst, RM and Wellems, TE. 2014. “Malaria (Plasmodium Species)”. In: Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Bennett, JE, Dolin, R, Blaser, MJ. 8th edition. Philadelphia: Elsevier Saunders. (Fairhurst and Wellems 2014, 3070–3090)
- Phillips, MA, Burrows, JN, Manyando, C, et al. 2017. Malaria. Nat Rev Dis Primers. 3: 17050. PMID: 28770814
- World Health Organization. 2019. World malaria report 2019. World Health Organization. https://www.who.int/publications/i/item/world-malaria-report-2019