When R 0 is considered in a spatial context, many of its properties fail to hold. In particular, diseases with R 0 > 1 can fail to persist, depending on the nature of the spatial transmission. Since many diseases are spatially dependent, this further limits the utility of R 0 . As R 0 increases beyond 1, the probability of disease invading the initially infected host group increases, but additional criteria are important to determining the probability of the spreading of the disease to other groups.