Life cycle of Pf. (A) During the blood meal of an infected Anopheles mosquito, sporozoites are injected into the human skin. (B) Sporozoites migrate through the blood stream to the liver and infect hepatocytes. In hepatocytes, the parasite multiplies and differentiates into asexual merozoites that rupture the infected host cell and enter the blood stream. (C) In the blood, merozoites infect erythrocytes for repeating rounds of asexual replication, erythrocyte lysis, and infection of fresh erythrocytes, resulting in exponential parasite growth associated with symptom onset and malaria disease. (D) Some merozoites differentiate into female and male gametocytes. These sexual erythrocytic parasites can be taken up by a mosquito during another blood meal for completion of the life cycle in the insect vector.