PAILIN, CAMBODIA—Whatever the reason, this is where it starts. Resistance to chloroquine surfaced here in the 1950s before sweeping through the wider Mekong region and then into India and Africa, causing millions of deaths. Sulfadoxine-pyrimethamine went next, in the 1960s. Mefloquine failed in the 1970s.
Then in late 2008 and 2009 came reports that rocked the malaria world: Artemisinin, the so-called wonder drug that has sent malaria deaths plummeting across the globe over the past decade, was losing its effectiveness here. That sparked global alarm and prompted an ultimately futile emergency plan to contain resistance in Cambodia before the last, best drug was lost.
Now, Pailin is the epicenter of what some say is the greatest threat yet to malaria control: the deadliest malaria parasite, Plasmodium falciparum, has become resistant not only to artemisinin, but to a key partner drug, piperaquine, or PPQ, that is used in combination with artemisinin and is critical to its success. The emergence of this MDR parasite is raising the specter of untreatable malaria in the Mekong region and perhaps beyond.