Role of Environmental Factors in Shaping Spatial Distribution of Salmonella enterica Serovar Typhi, Fiji
Ruklanthi de Alwis

, Conall Watson, Birgit Nikolay, John H. Lowry, Nga Tran Vu Thieu, Tan Trinh Van, Dung Tran Thi Ngoc, Kitione Rawalai, Mere Taufa, Jerimaia Coriakula, Colleen L. Lau, Eric J. Nilles, W. John Edmunds, Mike Kama, Stephen Baker, and Jorge Cano
Author affiliations: London School of Hygiene and Tropical Medicine, London, UK (R. de Alwis, C. Watson, B. Nikolay, W.J. Edmunds, J. Cano); Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam (R. de Alwis, N.T.V. Thieu, T.T. Van, D.T.T. Ngoc, S. Baker); Oxford University, Oxford, UK (R. de Alwis, S. Baker); University of the South Pacific, Suva, Fiji (J.H. Lowry); Project Heaven, Suva (K. Rawalai); Ministry of Health and Medical Services, Suva (M. Taufa, M. Kama); Fiji National University, Suva (J. Coriakula); Australian National University, Canberra, Australian Capital Territory, Australia (C.L. Lau); World Health Organization Western Pacific Region, Suva (E.J. Nilles); Brigham and Women’s Hospital, Boston, Massachusetts, USA (E.J. Nilles); Harvard Medical School, Boston (E.J. Nilles)
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Table 3
Relative contributions of predictor variables from an ensemble of 50 boosted regression tree models for typhoid fever seropositivity developed with cross-validation on data from 1,305 samples and 11 variables, Fiji
Variable |
Data type |
Relative contribution, % (95% CI) |
Age, y |
Continuous |
33.0 (31.1–34.8) |
Longitude, °E |
Continuous |
15.5 (14.7–16.0) |
Distance from major rivers and creeks, m |
Continuous |
14.5 (13.6–15.3) |
Annual rainfall, mm |
Continuous |
9.3 (8.5–10.0) |
Distance from flood-risk areas, m |
Continuous |
7.7 (6.8–8.4) |
Latitude, °S |
Continuous |
6.9 (5.6–7.9) |
Education |
Categorical |
4.2 (3.8–4.6) |
Urbanization |
Categorical |
3.3 (2.9–3.8) |
Typhoid fever vaccination |
Binary |
2.3 (2.1–2.5) |
Sewage disposal |
Categorical |
1.8 (1.5–2.2) |
Toilet type at home |
Categorical |
0.8 (0.6–1.2) |
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Page updated: January 17, 2018
Page reviewed: January 17, 2018
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