1 From the Department of Pathology, Division of Medical Microbiology (P.J.S.), the Department of Medicine, Division of Infectious Diseases (P.J.S.), and the Department of Biomedical Engineering (S.L.S.), Johns Hopkins School of Medicine, the Department of Computer Science and Center for Computational Biology, Whiting School of Engineering (S.L.S.), and the Department of Biostatistics, Bloomberg School of Public Health (S.L.S.), Johns Hopkins University, Baltimore.