A health worker checks a blood sample for malaria in the only hospital in Pailin in western Cambodia January 28, 2010. Bordering with Thailand, this former Khmer Rouge stronghold and dusty gem mining town is now better known for a malarial parasite that is worrying health experts in the region. Studies and research show artemisinin-based therapies - currently the most effective treatment against malaria - are taking longer to cure some of the patients. REUTERS/Damir Sagolj (CAMBODIA - Tags: HEALTH POLITICS SOCIETY)