Valerie T. J. Koh, Calvin J. Chiew, Khine Nandar, Anne Lee, Kelly Foo, Rachael Pung, Zubaidah Said, and Vernon Lee are with the Communicable Diseases Division, Ministry of Health, Singapore. Sean Wei Xiang Ong, Tau Hong Lee, David Chien Lye, and Yee-Sin Leo are with the National Centre for Infectious Diseases, Singapore. Lin Cui, Yi Kai Ng, and Raymond Lin are with the National Public Health Laboratory, National Centre for Infectious Diseases, Singapore.