1 Department of Medicine, Sheikh Khalifa Medical City, Abu Dhabi, United Arab Emirates; Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
2 Division of Infectious Diseases, University Medicine Cluster, National University Hospital, Singapore; Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
3 Department of Medicine, Walter Reed National Military Medical Center, Bethesda, Maryland.
4 Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: joeco@jhmi.edu.