This Manuscript is about a mosquito-borne viral disease that have a great impact in livestock and humans in Africa. The disease was first characterized by Daubney and his co-workers, Hudson and Garnham in 1934, while working at the Veterinary Research Laboratory at Kabete in Kenya. The work is on Molecular epidemiology of Rift Valley fever (RVF) and its socio-economic impacts. The manuscript gives a good overview on the molecular epidemiology of RVF using serum samples that were collected during the 2006/07 outbreaks in different areas of Tanzania. The socio-economic part uses the same outbreak to try to describe the effects that were associated with the outbreaks. The findings have shown that there were viruses of RVF circulating in the country that affected animals as well as human leading socio-economic effect at individual and national level.