[1] San Francisco State Univ, Dept Publ Hlth, San Francisco, CA USA
[2] Johns Hopkins Univ, Bloomberg Sch Publ Hlth, Dept Int Hlth, Baltimore, MD USA
[3] Drexel Univ, Sch Publ Hlth, Dept Epidemiol & Biostat, Philadelphia, PA USA
[4] Coll Hlth & Social Sci, Dept Publ Hlth, 1600 Holloway Ave, San Francisco, CA 94132 USA