1. Department of Preventive Medicine, Medical School, Federal University of Bahia, Salvador, Bahia, Brazil
2. Division of Infectious Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115
3. Hospital Professor Edgard Santos, Federal University of Bahia, Salvador, Bahia, Brazil
4. Department of Tropical Public Health, Harvard School of Public Health, Boston, Massachusetts 02115
5. Nucleo de Pesquisas, Fundação Oswaldo Cruz (F.O.C.), Salvador, Bahia, Brazil