1. a Department of Public Health, Medical College , Chang Gung University , Taoyuan , Taiwan
2. b Biostatistics Core Laboratory, Molecular Medicine Research Center , Chang Gung University , Taoyuan , Taiwan
3. c Section of Communicable Disease Control , Public Health Bureau of Taoyuan County , Taoyuan , Taiwan
4. d Department of Nursing , Chang Gung University of Science and Technology , Taoyuan , Taiwan