[1] Danish Epidemiol Sci Ctr, Statens Serum Inst, Dept Epidemiol Res, DK-2300 Copenhagen S, Denmark
[2] ORSTOM, Inst Francais Rech Sci Dev Cooperat, Dakar, Senegal
[3] ORSTOM, F-34032 Montpellier, France
[4] INSERM, U88, F-94415 St Maurice, France
[5] Univ Fann, Ctr Hosp, Clin Malad Infect Ibrahima Diop Mar, Dakar, Senegal
[6] Med Res Council Labs, Banjul, Gambia