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BIOLOGICAL SCIENCES / ECOLOGY
Mapping H5N1 highly pathogenic avian influenza risk in Southeast Asia
*Biological Control and Spatial Ecology, Université Libre de Bruxelles, CP160/12, Avenue FD Roosevelt 50, B-1050 Brussels, Belgium; Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, 39 College Road, Durham, NH 03824; Epidemiology Division, Department of Veterinary Clinical Sciences, The Royal Veterinary College, University of London, London AL9 7TA, United Kingdom; ¶Swiss National Center of Competence in Research North–South, 3012 Berne, Switzerland; ||Department of Livestock Development, Ministry of Agriculture and Cooperatives, Bangkok 10400, Thailand; **Regional Office for Asia and the Pacific, Food and Agriculture Organization of the United Nations, Bangkok 10200, Thailand; Department of Animal Health, Ministry of Agriculture and Rural Development, Hanoi, Vietnam; and Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome, Italy
Edited by Rita R. Colwell, University of Maryland, College Park, MD, and approved February 7, 2008 (received for review November 9, 2007)
The highly pathogenic avian influenza (HPAI) H5N1 virus that emerged in southern China in the mid-1990s has in recent years evolved into the first HPAI panzootic. In many countries where the virus was detected, the virus was successfully controlled, whereas other countries face periodic reoccurrence despite significant control efforts. A central question is to understand the factors favoring the continuing reoccurrence of the virus. The abundance of domestic ducks, in particular free-grazing ducks feeding in intensive rice cropping areas, has been identified as one such risk factor based on separate studies carried out in Thailand and Vietnam. In addition, recent extensive progress was made in the spatial prediction of rice cropping intensity obtained through satellite imagery processing. This article analyses the statistical association between the recorded HPAI H5N1 virus presence and a set of five key environmental variables comprising elevation, human population, chicken numbers, duck numbers, and rice cropping intensity for three synchronous epidemic waves in Thailand and Vietnam. A consistent pattern emerges suggesting risk to be associated with duck abundance, human population, and rice cropping intensity in contrast to a relatively low association with chicken numbers. A statistical risk model based on the second epidemic wave data in Thailand is found to maintain its predictive power when extrapolated to Vietnam, which supports its application to other countries with similar agro-ecological conditions such as Laos or Cambodia. The model's potential application to mapping HPAI H5N1 disease risk in Indonesia is discussed.
animal husbandry | epidemiology | remote sensing | spatial modeling
Author contributions: M.G., X.X., W.K., M.J.O., V.M., and J.S. designed research; M.G. performed research; M.G., X.X., D.U.P., M.E., S.B., C.C., P.C., and P.Q.M. analyzed data; and M.G., X.X., D.U.P., and J.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0710581105/DCSupplemental.
To whom correspondence should be addressed. E-mail: mgilbert{at}ulb.ac.be
© 2008 by The National Academy of Sciences of the USA
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