Researchers at the Johns Hopkins Bloomberg School of Public Health studying dengue hemorrhagic fever epidemics in Thailand have determined that the disease radiates outward in a traveling wave from Bangkok, the nation's largest city, to infect every province in the country. According to the researchers' analysis, the spatial-temporal wave travels at a speed of 148 kilometers per month and takes about eight months to spread through the entire country. The analysis appears in the January 22, 2004, edition of the journal Nature.
"We used a new mathematical technique developed by NASA for analysis of waves in physical materials – like water waves and sound waves – to study "epidemic waves" of dengue cases. Our study is the first step to understanding the mechanism of how a disease like dengue spreads through the country," said lead author Derek Cummings, a PhD candidate at the Johns Hopkins University's Bloomberg School of Public of Health and Whiting School of Engineering. "Anticipating dengue epidemics and determining the causes of those epidemics could help us plan control strategies more effectively."
Dengue fever is a mosquito-borne illness that infects 50 million to 100 million people worldwide each year, many of them children. Epidemics of the most serious and life-threatening form of the disease, dengue hemorrhagic fever, place a heavy burden on public health systems.
The number of cases of dengue hemorrhagic fever in Thailand varies widely from year to year. Cummings and his colleagues examined the spatial-temporal dynamics of dengue hemorrhagic fever in a data-set describing 850,000 infections that occurred between 1983 and 1997. Their analysis showed that outbreaks in provinces surrounding Bangkok were either synchronous or lag behind Bangkok, which indicated a repeating, spatial-temporal wave emanating from the city. The researchers do not know exactly why the wave occurs, but they believe it is related to the movement of people. Bangkok is heavily populated and it is the cultural and economic center of Thailand.
"Disease surveillance and control in Bangkok may help surrounding regions prepare for future outbreaks of dengue fever. Our results suggest that high priority should be placed on surveillance and control systems in urban areas of Southeast Asia," said Donald S. Burke, MD, co-author of the study and professor of International Health at the School of Public Health.
"Traveling waves in the occurrence of dengue hemorrhagic fever in Thailand" was written by Derek A.T. Cummings, Rafael A. Irizarry, Norden E. Huang, Timothy P. Endy, Ananda Nisalak, Kummuan Ungchusak and Donald S. Burke.
Research was supported by grants from the National Oceanic and Atmospheric Administration's Joint Program on Climate Variability and Human Health and the Bill and Melinda Gates Foundation.
Materials provided by Johns Hopkins University Bloomberg School Of Public Health. Note: Content may be edited for style and length.
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