1. From the Swiss Tropical and Public Health Institute, Allschwil, and the University of Basel, Basel — both in Switzerland (E.C.M., S.W., J.H., J.K.); and Ifakara Health Institute, Ifakara (E.C.M.), and Public Health Laboratory Ivo de Carneri, Chake Chake, Pemba (S.M.A.) — both in Tanzania.