One of the successes was the development in the 1970s of the antimalarial drug artemisinin, which is a processed extract of "Artemisia annua", a herb traditionally used as a fever treatment. Artemisia annua has been used by Chinese herbalists in traditional Chinese medicines for 2,000 years. In 1596, Li Shizhen recommended tea made from qinghao specifically to treat malaria symptoms in his "Compendium of Materia Medica". Researcher Tu Youyou discovered that a low-temperature extraction process could isolate an effective antimalarial substance from the plant. Tu says she was influenced by a traditional Chinese herbal medicine source, "The Handbook of Prescriptions for Emergency Treatments", written in 340 by Ge Hong, which states that this herb should be steeped in cold water. The extracted substance, once subject to detoxification and purification processes, is a usable antimalarial drug – a 2012 review found that artemisinin-based remedies were the most effective drugs for the treatment of malaria. For her work on malaria, Tu received the 2015 Nobel Prize in Physiology or Medicine. Despite global efforts in combating malaria, it remains a large burden for the population. Although WHO recommends artemisinin-based remedies for treating uncomplicated malaria, artemisinin resistance can no longer be ignored.