Apart from the epidemics that results from unusual high precipitation that leads to widespread flooding, a pre-condition for Rift Valley fever (RVF) to occur; low-level inter-epidemic transmission of RVF occurs regularly throughout much of the African continent. However, most of such transmissions remain unrecognized due to inadequate surveillance in the continent. The main goal of this research is to study recent and longer standing infection with RVF in both people and livestock. The exposure status in livestock and people will be coupled with vector mosquito studies in the same localities. This research work is set in the seasonal flooding plains of the Kilombero river valley which mimics unusual precipitation increase on annual basis. The output from this work will help to better define and understand the interaction between spatial living environment, human behavior and migration on the risk for inter-epidemic and epidemic transmission of RVF.