The last three decades have seen a spread of the most dangerous forms of the Plasmodium falciparum parasite—those resistant to drugs. The first observed resistance was against cholorquinine (CQ)—the drug of choice throughout most of the 20th century. Resistance to a sulfadoxine-pyrimethamine (SP) spread throughout the 1980s. By 2009, only five years after the World Health Organization approved artemisinin (ART) as a front-line malaria treatment, ART-resistant parasites had appeared along the Cambodia-Thailand border. Scientists are still trying to devise new treatments and vaccines to eliminate malaria worldwide. Colors on the map indicate areas with parasites resistant to the corresponding drug or drugs.

Source: WorldWide Antimalarial Resistance Network (WWARN, www.wwarn.org)