The extensive networks of frequent population mobility in the Samoan Islands and their implications for infectious disease transmission

Population mobility has been demonstrated to contribute to the persistent transmission and global diffusion of epidemics. In the Pacific Islands, population mobility is particularly important for emerging infectious diseases, disease elimination programs, and diseases spread by close contact. The extent of population mobility between American Samoa villages, Samoa districts and other countries was investigated based on travel data collected during community surveys in American Samoa in 2010 and 2014. Within American Samoa, workers commuted daily across the whole of the main island of Tutuila, with work hubs drawing from villages across the island. Of the 670 adult workers surveyed, 37% had traveled overseas in the past year, with 68% of trips to Samoa. Of children aged 8-13 years (n = 337), 57% had traveled overseas, with 55% of trips to Samoa. An extensive network of connections between American Samoa villages and Samoa districts was demonstrated, with most trips lasting one week to one month. Our study showed that populations in the Samoan islands are highly mobile, and quantified the extent and destinations of their travels. Our findings offer insight into the impact of population mobility on the transmission of infectious diseases and data to refine existing models of disease transmission in the Pacific islands.Te 2014 study was funded by grants from the Australian Institute of Tropical Health and Medicine (http://www.aithm.jcu.edu.au/, #13122014) and the Faculty of Medicine and Biomedical Sciences at the University of Queensland (http://www.uq.edu.au, #2127835). ZX was funded by a National Health and Medical Research Council (NHMRC) Centre of Research Excellence. CLL was supported by an NHMRC Fellowship (1109035). James Cook University and GlaxoSmithKline provided fnancial support for the WHO Collaborating Centre for Lymphatic Filariasis, Soil-Transmitted Helminths, and Other Neglected Tropical Diseases at James Cook University, Cairns, Australia. Te funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript