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

Abstract

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.

Demographic, socioeconomic and disease knowledge factors, but not population mobility, associated with lymphatic filariasis infection in adult workers in American Samoa in 2014

“…Culturally, people in the Pacific Islands generally spend a significant amount of time outdoors and have close contact with their environment. While the vectors have a short flight range, people in American Samoa, as in other Pacific Islands, are highly mobile, both on a daily commuting basis to work at major employers [2] and to Samoa, other Pacific Islands and the USA, especially Hawaii. Other potential risk factors, such as population or household size and density, income/ socioeconomic status, or work location (indoor or outdoor) [11] are not well studied.…”

“…The age distribution of sampled participants was previously shown to be similar to the distribution in the working population [2], but different to the general population (Additional file 1: Figure S1). Due to zero positives in some 10-year age groups, age-adjusted prevalence was estimated using two age groups: 15-34 and ≥ 35 years.…”

“…Although American Samoa is geographically isolated, the population is highly mobile and travel frequently to visit family and friends, and for work, study and recreation. However, most families live on ancestral land, and permanent relocations within the territory are relatively rare [2]. American Samoa is divided administratively into 9 counties, each consisting of several villages [23].…”

“…Of these, 33.6% went to Samoa, 4.6% to other countries that were LF endemic at that time (Fiji, Tonga and Palau) and 9.9% to non-endemic overseas destinations (Hawaii, mainland USA, New Zealand, Australia, Japan). Some travellers made multiple overseas trips (mean 1.45, range 1-6 [2]), so the proportion of persons traveling to either Samoa or other endemic countries in the last year was 35.0%. In addition, 40.7% of households received visitors (who stayed at least one night) from Samoa in the last year.…”

“…The population was estimated at 61,181 in 2014 [1]. There are close family and cultural ties to nearby Samoa (formerly Western Samoa) with extensive and frequent movement of people in both directions for shortand long-term visits [2], as well as to and from Hawaii and mainland USA.…”