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Jonathan A. Patz, ¹ Willem J.M. Martens, ² Dana A. Focks, ³ and Theo H. Jetten ⁴

¹ Department of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205-2179 USA
² Department of Mathematics, Maastricht University, Maastricht, The Netherlands
³ Center for Medical, Agricultural and Veterinary Entomology, Agricultural Research Service, U.S. Department of Agriculture, Gainesville, FL 32604 USA
⁴ Department of Entomology, Graduate School for Production Ecology, Wageningen Agricultural University, Wageningen, The Netherlands

Abstract

Climate factors influence the transmission of dengue fever, the world's most widespread vector-borne virus. We examined the potential added risk posed by global climate change on dengue transmission using computer-based simulation analysis to link temperature output from three climate general circulation models (GCMs) to a dengue vectorial capacity equation. Our outcome measure, epidemic potential, is the reciprocal of the critical mosquito density threshold of the vectorial capacity equation. An increase in epidemic potential indicates that a smaller number of mosquitoes can maintain a state of endemicity of disease where dengue virus is introduced. Baseline climate data for comparison are from 1931 to 1980. Among the three GCMs, the average projected temperature elevation was 1.16°C, expected by the year 2050. All three GCMs projected a temperature-related increase in potential seasonal transmission in five selected cities, as well as an increase in global epidemic potential, with the largest area change occurring in temperate regions. For regions already at risk, the aggregate epidemic potential across the three scenarios rose on average between 31 and 47% (range, 24-74%) . If climate change occurs, as many climatologists believe, this will increase the epidemic potential of dengue-carrying mosquitoes, given viral introduction and susceptible human populations. Our risk assessment suggests that increased incidence may first occur in regions bordering endemic zones in latitude or altitude. Endemic locations may be at higher risk from hemorrhagic dengue if transmission intensity increases. Key words : Aedes , biological models, climate, dengue, greenhouse effect, risk assessment, virus diseases. Environ Health Perspect 106:147-153 (1998) . [Online 3 February 1998]

http://ehpnet1.niehs.nih.gov/docs/1998/106p147-153patz/ abstract.html

Address correspondence to J.A. Patz, Division of Occupational and Environmental Health, Johns Hopkins School of Hygiene and Public Health, 615 North Wolfe Street, Room 7041, Baltimore, MD 21205-2179 USA.

Partial funding support came from the Climate Policy and Assessment Division, EPA, cooperative CR823143 ; the National Institute of Public Health and Environment, the Netherlands ; and the Center for Medical, Agricultural and Veterinary Entomology, USDA. We thank Mark Wilson, Department of Epidemiology, University of Michigan, for his insightful comments.

Received 23 June 1997 ; accepted 3 November 1997.