EMPIRICAL DETERMINANTS OF MEASLES METAPOPULATION DYNAMICS IN ENGLAND AND WALES

A key issue in metapopulation dynamics is the relative impact of inter nal patch dynamics and coupling between patches. This problem can be a ddressed by analysing large spatiotemporal data sets, recording the lo cal and global dynamics of metapopulations. In this paper, we analyse the dynamics of measles metapopulations in a large spatiotemporal case notification data set, collected during the pre-vaccination era in En gland and Wales. Specifically, we use generalized linear statistical m odels to quantify the relative importance of local influences (birth r ate and population size) and regional coupling on local epidemic dynam ics. Apart from the proportional effect of local population size on ca se totals, the models indicate patterns of local and regional dynamic influences which depend on the current state of epidemics. Birth rate and geographic coupling are not associated with the size of major epid emics. By contrast, minor epidemics-and especially the incidence of lo cal extinction of infection-are influenced both by birth rate and geog raphical coupling. Birth rate at a lag of four years provides the best fit, reflecting the delayed recruitment of susceptibles to school coh orts. A hierarchical index of spatial coupling to large centres provid es the best spatial model. The model also indicates that minor epidemi cs and extinction patterns are more strongly influenced by this region al effect than the local impact of birth rate.