[1] Johns Hopkins Univ, Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD 21205 USA
[2] Johns Hopkins Med Inst, Dept Internal Med, Baltimore, MD 21287 USA
[3] Chinese Peoples Liberat Army Gen Hosp, Dept Emergency Med, Beijing 100853, Peoples R China
[4] Johns Hopkins Med Inst, Dept Ophthalmol, Baltimore, MD 21287 USA
[5] New York Acad Med, Ctr Urban Epidemiol Studies, New York, NY 10029 USA
[6] Johns Hopkins Univ, Bloomberg Sch Publ Hlth, Dept Microbiol & Mol Immunol, Baltimore, MD 21205 USA