Obtaining economic data about the incidence and prevalence of disease are essential for estimating the costs and benefits of strengthening and maintaining prevention and control programmes, improving existing surveillance systems, and introducing other proposed interventions, such as vaccines. To ascertain the financial costs to countries and individuals of vector and rodent-borne diseases many different aspects must be taken into account; one would have to determine the medical costs to the affected person which would include medical care, the costs of hospitalization, if necessary, and the cost of losses in productivity caused by illness and premature death. The costs to local or national governments might include all aspects of medical care depending on the health system of the given country or community, the cost of epidemiological investigations and the costs involved in the control of the arthropod vectors or rodent reservoir hosts of disease. The number of mosquito control organizations in Europe is rapidly growing while other groups are responsible for the control of tick vectors. An attempt to determine such costs would be a major undertaking and beyond the scope of this book. Nevertheless such costs are real and are a severe ‘burden’ on the individual and on the community. Some examples will be given below of instances in which the costs of vector- or rodent-borne disease outbreaks have been calculated.