There are four distinctly different types of malaria. Plasmodium vivax is the most widespread type, but it is rarely fatal. The rarest of all types, Plasmodium ovale, only occurs in certain areas of West Africa. Plasmodium malariae has a wide area of distribution but is fairly rare, and Plasmodium falciparum is not only widespread but also the most deadly of the different types of malaria.
The most widespread of all, P. vivax, can be found in Central and South America, Southeast Asia, and throughout India. Parasites responsible for this type of malaria can remain dormant in the liver for months or even years, making some cases hard to diagnose because previous exposure can be overlooked once symptoms finally develop. Some strains have become resistant to anti-malarial drugs, making it increasingly difficult to treat the 70 to 80 million cases that develop each year.
P. ovale is the rarest of all the types of malaria, found only in tropical areas of West Africa. Those bitten by mosquitoes carrying the malaria parasite can develop symptoms at any time up to four years after being bitten, as the parasites incubate in the liver before attacking the red blood cells. Sometimes this variety partners with another type of malaria, resulting in a dual infection.
Affecting not only humans but also dogs, P. malariae is also fairly rare. Found throughout tropical and subtropical areas in Africa, Southeast Asia, and Central and South America, it has a wide area of distribution but is not particularly prevalent. As with P. vivax, contracting this form of malaria rarely results in death.
The most deadly of the different types of malaria is P. falciparum. Approximately 90% of malaria-related deaths come from an infection of this type; death can happen as soon as a few hours after exposure. With as wide a distribution area as P. malariae, there are millions of reported cases every year, mostly from Africa. Even in cases that do not result in death, infections and symptoms are severe.
Symptoms for all forms of malaria are similar, and include fever, headache, convulsions, chills, muscle pain, sweating, vomiting, and nausea. In severe cases, the infected individual can fall into a coma. For the three less severe forms of malaria, prognosis is generally good. Complications are generally seen in cases of P. falciparium, including liver and kidney failure, meningitis, respiratory failure or rupturing of the spleen, and internal bleeding. There are an estimated 300 to 500 million cases each year of all types of malaria, and more than 1 million of those are fatal.