Spatio-temporal dynamics of measles outbreaks in Cameroon

Purpose: In 2012, Cameroon experienced a large measles outbreak of over 14,000 cases. To determine the spatio-temporal dynamics of measles transmission in Cameroon, we analyzed weekly case data collected by the Ministry of Health. Methods: We compared several multivariate time-series models of population movement to characterize the spatial spread of measles in Cameroon. Using the best model, we evaluated the contribution of population mobility to disease transmission at increasing geographic resolutions: region, department, and health district. Results: Our spatio-temporal analysis showed that the power law model, which accounts for long-distance population movement, best represents the spatial spread of measles in Cameroon. Population movement between health districts within departments contributed to 7.6% (range: 0.4%–13.4%) of cases at the district level, whereas movement between departments within regions contributed to 16.0% (range: 1.3%–23.2%) of cases. Long-distance movement between regions contributed to 16.7% (range: 0.1%–59.0%) of cases at the region level, 20.1% (range: 7.1%–30.0%) at the department level, and 29.7% (range: 15.3%–47.6%) at the health district level. Conclusions: Population long-distance mobility is an important driver of measles dynamics in Cameroon. These findings demonstrate the need to improve our understanding of the roles of population mobility and local heterogeneity of vaccination coverage in the spread and control of measles in Cameroon.