International Journal of Molecular Sciences Article A Melting Curve-Based Multiplex RT-qPCR Assay for Simultaneous Detection of Four Human Coronaviruses Zhenzhou Wan 1,2,†, Ya’nan Zhang 1,†, Zhixiang He 1, Jia Liu 1, Ke Lan 1, Yihong Hu 1,* and Chiyu Zhang 1,* 1 Pathogen Diagnostic Center, CAS Key Laboratory of Molecular Virology & Immunology, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai 200025, China;