" The four known for targeting humans are transmitted from person to person by Anopheles mosquitoes. These four parasites possess wondrously complicated life histories, encompassing multiple metamorphoses and different forms in series: an asexual stage known as the sporozoite, which enters the human skin during a mosquito bite and migrates to the human liver; another asexual stage known as the merozoite, which emerges from the liver and reproduces in red blood cells; a stage known as the trophozoite, feeding and growing inside the blood cells, each of which fattens as a schizont and then bursts, releasing more merozoites to further multiply in the blood, and causing a spike of fever; a sexual stage known as the gametocyte, differentiated into male and female versions, which emerge from a later round of infected red blood cells, enter the bloodstream en masse, and are taken up within a blood meal by the next mosquito; a fertilized sexual stage known as the ookinete, which lodges in the gut lining of the mosquito, each ookinete ripening into a sort of egg sac filled with sporozoites; and then come the sporozoites again, bursting out of the egg sac and migrating to the mosquito’s salivary glands, where they lurk, ready to surge down the mosquito’s proboscis into another host. "

― David Quammen , Spillover: Animal Infections and the Next Human Pandemic