As mentioned above, the NWS conducts nationwide surveillance for tornado-related injuries and deaths, but this system collects very little additional information on personal safety-seeking behavior, the degree of warning that occurred, or people's access to shelter. Although some case-control studies of risk factors associated with tornado-related death and injury have been done, most have lacked the type of multidisciplinary approach needed for good epidemiologic studies, with few incorporating contributions from epidemiology, wind engineering, and meteorology.