Duelling timescales of host movement and disease recovery determine invasion of disease in structured populations

The epidemic potential of a disease is traditionally assessed using the basic reproductive number, R-0. However, in populations with social or spatial structure a chronic disease is more likely to invade than an acute disease with the same R-0, because it persists longer within each group and allows for more host movement between groups. Acute diseases 'perceive' a more structured host population, and it is more important to consider host population structure in analyses of these diseases. The probability of a pandemic does not arise independently from characteristics of either the host or disease, but rather from the interaction of host movement and disease recovery timescales. The R-* statistic, a group-level equivalent of R-0, is a better indicator of disease invasion in structured populations than the individual-level R-0.