Re‐infection of healthy cassava plants by African cassava mosaic virus (ACMV) was followed In different varieties and for several years at various locations in two regions of Ivory Coast. Whitefly populations on cassava and virus incidence varied widely between sites, even amongst those close to one another. However, for each location and in every year, the spread of ACMV showed the same general trend. Little spread occurred at Toumodi in the savannah region which is outside the main cassava production area. Much greater spread occurred at a nearby site and at all sites in the forest region except one alongside the ocean where there were no cassava plantings upwind. Among sites there was no direct relation between virus incidence and the total number of adult whitefly, whereas there was a relationship between spread and the occurrence of infected cassava upwind although not necessarily close by.