Acute infections of P. vivax have traditionally responded well to a treatment course of chloroquine for the systemic erythrocytic infection. However, in the Indonesian archipelago, sensitivity of the parasite to chloroquine appears to be diminished; therefore, chloroquine is no longer used as a standard treatment. Chloroquine-resistant P. vivax also appears to be expanding its territory in SE Asia. For these reasons, treatment in this region as well as Solomon Islands, Vanuatu and now Cambodia is shifting more towards artemisinin combination therapies (ACTs). The advantage of ACTs is the circumvention of chloroquine resistance and the ability to treat falciparum malaria, should a patient have a mixed Plasmodium spp infection.