1. Department of Pediatrics; the 2nd Affiliated Hospital of Kunming Medical University; Kunming Yunnan 650000 China
2. Epidemiology Unit, Faculty of Medicine; Prince of Songkla University; Hat Yai Songkhla 90110 Thailand
3. Department of Pediatrics, Faculty of Medicine; Prince of Songkla University; Hat Yai Songkhla 90110 Thailand
4. Department of Pediatrics; Yunnan Provincial Hospital of Traditional Chinese Medicine; Kunming Yunnan 650000 China
5. Department of Pediatrics; Yan'an Hospital of Kunming City; Kunming Yunnan 650000 China