Malaria, sometimes called “frios’ (chills), is a disease of animals, especially birds, monkeys and humans, caused by the infection by protozoan of the genus Plasmodium and characterized by chills.  These are transmitted by the bite of about 60 species of mosquitoes of the genus Anopheles. The disease may occur in subtropical and tropical regions in almost all parts of the world as well as in other temperature areas.

Human Malaria occurs in four forms, each caused by a different species of parasite. In each form, the symptoms usually are chills, fever and sweating. In untreated cases, these attacks recur periodically.

• Tertian malaria is the mildest form caused by Plasmodium vivax, in which the fever may occur about every second day after the initial attack (which may occur within two weeks after infection.)

• Jungle fever, malignant tertian malaria, or estivo-antumnal malaria, caused by Plasmodium falciparum, is responsible for most of the deaths from Malaria. The organisms in this form of the disease often block the blood vessels of the brain, producing coma, delirium, and finally death.

• Quartan malaria, caused by Plasmodium malaria, has a longer incubation period than either tertian malaria or jungle fever, the first attack does not appear until 18 to 40 days after infection. The attacks recur about every third day.

• Plasmodium ovale is similar to benign tertian malaria. In all forms of the disease, periodic fevers may be less regularly spaced in some people.

During the incubation period of malaria, the protozoan grows within cells in the liver, a few days before the first attack. The organisms invade the red blood cells, which they destroy in the course of their development, producing the typical febrile attack.

Malaria is transmitted to a human by the bite of an infected female Anopheles mosquito. The mosquito becomes infected by ingesting the blood of a human infected with malaria. Of the 1.8 billion persons at risk of malaria worldwide, there are an estimated 500 million clinical cases and nearly 3.5 million deaths each year. It is, therefore, one of the most important infectious diseases in the world.