Ming-Hsun Bryan Keng1, Hui-Lin Clara Keng2, Ban-Hock Tan3, Gee-Chuan Wong4. 1. a Yong Loo Lin School of Medicine, National University of Singapore , Singapore , Singapore. 2. b Raffles Institution , Singapore , Singapore. 3. c Department of Infectious Diseases , Singapore General Hospital , Singapore , Singapore. 4. d Department of Hematology , Singapore General Hospital , Singapore , Singapore.