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Simon Hales,¹ Phil Weinstein,¹ Yvan Souares,² and Alistair Woodward¹

¹Department of Public Health, Wellington School of Medicine, Wellington, New Zealand
²Community Health Programme, Secretariat of the Pacific Community, Noumea, New Caledonia

Abstract

The objective of the study was to investigate the relationship between reported incidence of dengue fever and El Niño southern oscillation (ENSO) in 14 island nations of the South Pacific. Using a mixed ecological study design, we calculated correlations between annual averages of the southern oscillation index (SOI) , local temperature and rainfall, and dengue fever. We also calculated temporal correlations between monthly reports of dengue fever cases on different islands. There were positive correlations between SOI and dengue in 10 countries. In five of these (including all of the larger islands) there were also positive correlations between SOI and estimates of local temperature and/or rainfall. There were temporal correlations between monthly reports of dengue cases within two groups of countries. Climate changes associated with ENSO may trigger an increase in dengue fever transmission in larger, more populated islands where the disease is endemic. There was also evidence of propagation of infection from larger islands to smaller neighbors. Unlike the initiation of epidemics, this transfer between islands appears to be independent of interannual climate variations, pointing to the importance of modulating factors in dengue transmission such as population density and travel. In the future, models of the impact of climate change must attempt to account for these factors. Key words: climate, dengue, disease vectors, El Niño, environment, epidemiology, southern oscillation. Environ Health Perspect 107:99-102 (1999) . [Online 5 January 1999]

http://ehpnet1.niehs.nih.gov/docs/1999/107p99-102hales/ abstract.html

Address correspondence to S. Hales, Department of Public Health, Wellington School of Medicine, Mein St., Wellington, New Zealand.

We thank the Community Health Programme, Secretariat of the Pacific Community, Noumea, for the dengue notification data ; Benno Blumenthal at the International Research Institute for climate prediction for providing access to the NCAR/NCEP reanalysis data ; Phil Jones, C. Ropelewski, R. Allan, and the Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, UK, for the SOI dataset ; and the Distributed Active Archive Center at the Goddard Space Flight Center for distributing this.

S.H. is funded by a Health Research Council of New Zealand training fellowship.

Received 2 July 1998 ; accepted 20 August 1998.