title: Travelling waves in the occurrence of dengue haemorrhagic fever in Thailand.
abstract: Dengue fever is a mosquito-borne virus that infects 50-100 million people each year. Of these infections, 200,000-500,000 occur as the severe, life-threatening form of the disease, dengue haemorrhagic fever (DHF). Large, unanticipated epidemics of DHF often overwhelm health systems. 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 decomposition 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. 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.
authors.affiliation: Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Derek A T
authors.initials: DA
authors.lastname: Cummings
authors.forename: Rafael A
authors.initials: RA
authors.lastname: Irizarry
authors.forename: Norden E
authors.initials: NE
authors.lastname: Huang
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Endy
authors.forename: Ananda
authors.initials: A
authors.lastname: Nisalak
authors.forename: Kumnuan
authors.initials: K
authors.lastname: Ungchusak
authors.forename: Donald S
authors.initials: DS
authors.lastname: Burke
mesh_terms: D005843:Geography; D006801:Humans; D015994:Incidence; D019595:Severe Dengue / Q000453:epidemiology*; D013785:Thailand / Q000453:epidemiology; D013997:Time Factors