DEFINITION & LIFE CYCLE
Malaria is an infectious disease caused by protozoans of the genus Plasmodium, and is transmitted by the bite of infected Anopheles mosquitoes. The species P. falciparum accounts for the preponderance of global morbidity and mortality, and 41 percent of the world's population live in areas where malaria is endemic.¹ Malaria is a preventable and treatable disease but it is estimated to kill one to three million people each year, primarily young children.

To complete its life cycle the malaria parasite, Plasmodium, relies on two hosts, the female Anopheles mosquito and humans. The Plasmodium protozoa, the causative agent of malaria, is transmitted through the bite of an infected Anopheles mosquito to a human host. The parasites undergo many asexual replicative stages within the human host. One blood stage form (gametocyte) is transferred to the mosquito when the mosquito bites an infected human host. Once inside the mosquito, the parasite replication cycle is completed.

The life cycle of the malaria parasite is outlined below: 

• Anopheles mosquito infected with malaria sporozoites bites a human.
• Plasmodium sporozoites enter the bloodstream and travel to the liver, where they invade liver cells and divide.
• New morphological stages of the parasite called merozoites emerge from the liver and infect red blood cells.
• Merozoites infect red blood cells and rapidly replicate.
• Some merozoites in red blood cells develop into a sexual form called gametocytes.
• When an Anopheles mosquito bites the infected person, it ingests these gametocytes.
• In the mosquito's digestive system, the gametes combine to form a zygote.
• The zygote goes through several developmental stages to form sporozoites.
• The sporozoites migrate to the salivary glands of the mosquito.
• When the insect bites another person, the cycle begins again.

INFECTION CHARACTERISTICS
In most cases of Plasmodium infection, the incubation period is approximately seven to 30 days, but can be longer. The most malignant (P. falciparum) cases generally develop within one to two months of initial infection, while infections transmitted by P. vivax and P. ovale may not appear for six months or longer.²

In uncomplicated malaria, Plasmodium-infected patients may have flu-like symptoms, such as tiredness, fever, chills, diarrhea, vomiting, and general malaise. Plasmodium falciparum can cause complicated, or severe, malaria in which infected patients exhibit more critical symptoms such as severe anemia, respiratory distress, seizures, coma, and other neurological abnormalities. Severe malaria may occur in any individual with P. falciparum malaria but most often occurs in those individuals who have little or no immunity to the malaria parasite, such as young children or travelers to malaria-endemic areas.