Current malaria status and distribution of drug resistance in East and Southeast Asia with special focus to Thailand

Malaria is the world's most important parasitic infection ranking among the major health and developmental challenges. Despite years of continual efforts, malaria is still one of the major causes of morbidity and mortality affecting third-world countries and still a threat to over 2 billion people, representing approximately 40% of the world's population in about 100 countries (Rollback Malaria 2005). During the "eradication era", half a century ago, malaria was eliminated or effectively suppressed in many parts of the world, particularly subtropical regions. The disease is now on the rise again since it is appearing in areas where it had disappeared. The disaster can largely be attributed to antimalarial drug resistance in most malaria endemic countries. Geographical distribution of the disease is worldwide, being found in tropical areas, throughout sub-Saharan Africa and to a lesser extent in South Africa, Southeast Asia, the Pacific Islands, India and Central and South America. Best estimates currently describe the annual global burden of malaria as 300-500 million cases and 1-2 million deaths. Over 90% of the disease burden is in sub-Saharan Africa. The malaria burden differs according to age and gender; almost all deaths occur in African children under 5 years of age (Snow et al. 2001). Pregnant women in Africa (especially primigravidae) are at high risk, and are the major adult risk group in the continent. An increasing number of imported cases of malaria have been reported particularly as a result of increasing worldwide travel to regions where there is ongoing risk of malaria transmission. Nowadays, cases of malaria acquired by international travelers from developed countries probably number 25,000 cases per year, with 10,000 of them reported annually and approximately 150 deaths per year.