1. Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA;
2. Henry M. Jackson Foundation, Rockville, Maryland, USA;
3. Johns Hopkins Cameroon Program, Yaoundé, Cameroon;
4. Johns Hopkins Cameroon Program, Yaoundé, Cameroon;Army Health Research Center (CRESAR), Yaoundé, Cameroon;
5. Walter Reed Army Institute of Research, Rockville, Maryland, USA