To simplify and improve the effectiveness of human trypanosomosis control efforts as well as reduce their cost, it is desirable to identify high-risk sites for transmission of trypanosomes by tsetse flies to humans. The authors propose a simplification of the risk index previously developed by Laveissière et al. (1994). The simplified index has been developed in Côte d'Ivoire and validated in Cameroon. Unlike the old index which required determination of the flies' daily survival rate, the calculation of this new index requires only the knowledge of the proportions of teneral flies and of flies that have fed on human blood, from the population caught in the various biotopes.
