This study was supported in part by research grants 30660064 and 30872343 from National Natural Science Foundation of China; in part by research grant 0728137 from Natural Science Foundation of Guangxi Zhuang Autonomous Zone; and in part by research grant 200621 from the Bureau of Health, Guangxi Zhuang Autonomous Zone, China. . Published on December 1, 2008 as doi: 10.1183/09031936.00111908 ER...
