Artemisinin is a frontline drug in the fight against malaria. It's used around the world, and can clear the infection in just a few days. But reports of resistance began to emerge in western Cambodia in 2008, and this is now spread to other areas in South East Asia. To investigate, scientists sequenced the genomes of more than 800 malaria-causing parasites collected from all around the world. They found that some of the strains present in Cambodia were significantly different to the rest, and these were able to withstand artemisinin treatment. The researchers don't yet know how the parasites are beating the drugs. But they say understanding their genetic fingerprint will help them to quickly detect and track these strains if they spread.