1. Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
2. Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
3. Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
4. Laboratory for Hydrospheric Processes/Oceans and Ice Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
5. Virology Division, United States Army Medical Research Institute in Infectious Disease, Fort Detrick, Maryland 21702, USA
6. Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok 10400, Thailand
7. Bureau of Epidemiology, Ministry of Public Health, Nonthaburi 11000, Thailand

Correspondence to: Donald S. Burke² Email: dburke@jhsph.edu

Abstract

Dengue fever is a mosquito-borne virus that infects 50–100 million people each year¹. Of these infections, 200,000–500,000 occur as the severe, life-threatening form of the disease, dengue haemorrhagic fever (DHF)². Large, unanticipated epidemics of DHF often overwhelm health systems³. An understanding of the spatial–temporal pattern of DHF incidence would aid the allocation of resources to combat these epidemics. Here we examine the spatial–temporal dynamics of DHF incidence in a data set describing 850,000 infections occurring in 72 provinces of Thailand during the period 1983 to 1997. We use the method of empirical mode decomposition⁴ to show the existence of a spatial–temporal travelling wave in the incidence of DHF. We observe this wave in a three-year periodic component of variance, which is thought to reflect host–pathogen population dynamics^{5, 6}. The wave emanates from Bangkok, the largest city in Thailand, moving radially at a speed of 148 km per month. This finding provides an important starting point for detecting and characterizing the key processes that contribute to the spatial–temporal dynamics of DHF in Thailand.

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