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. 2008 May 28;3(5):e2268.
doi: 10.1371/journal.pone.0002268.

Environmental factors contributing to the spread of H5N1 avian influenza in mainland China

Li-Qun Fang  1 , Sake J de Vlas, Song Liang, Caspar W N Looman, Peng Gong, Bing Xu, Lei Yan, Hong Yang, Jan Hendrik Richardus, Wu-Chun Cao
Affiliations

Environmental factors contributing to the spread of H5N1 avian influenza in mainland China

Li-Qun Fang et al. PLoS One. .

Abstract

Background: Since late 2003, highly pathogenic avian influenza (HPAI) outbreaks caused by infection with H5N1 virus has led to the deaths of millions of poultry and more than 10 thousands of wild birds, and as of 18-March 2008, at least 373 laboratory-confirmed human infections with 236 fatalities, have occurred. The unrestrained worldwide spread of this disease has caused great anxiety about the potential of another global pandemic. However, the effect of environmental factors influencing the spread of HPAI H5N1 virus is unclear.

Methodology/principal findings: A database including incident dates and locations was developed for 128 confirmed HPAI H5N1 outbreaks in poultry and wild birds, as well as 21 human cases in mainland China during 2004-2006. These data, together with information on wild bird migration, poultry densities, and environmental variables (water bodies, wetlands, transportation routes, main cities, precipitation and elevation), were integrated into a Geographical Information System (GIS). A case-control design was used to identify the environmental factors associated with the incidence of the disease. Multivariate logistic regression analysis indicated that minimal distance to the nearest national highway, annual precipitation and the interaction between minimal distance to the nearest lake and wetland, were important predictive environmental variables for the risk of HPAI. A risk map was constructed based on these factors.

Conclusions/significance: Our study indicates that environmental factors contribute to the spread of the disease. The risk map can be used to target countermeasures to stop further spread of the HPAI H5N1 at its source.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Spatial distribution of HPAI H5N1 outbreaks in domestic poultry and wild birds and human cases in mainland China.
Poultry density is indicated by color gradient. Distributions of generalized migration routes of migratory birds are overlapped.
Figure 2
Figure 2. Predictive risk map of HPAI H5N1 outbreaks in birds.
The predictive risk map shows increased risk of HPAI H5N1 outbreaks in poultry and wild birds by color gradient. Locations of HPAI H5N1 outbreaks in poultry from January of 2007 to March 13, 2008 are also indicated (8 HPAI H5N1 outbreaks in mainland China).
Figure 3
Figure 3. Spatial random sampling for the case-control design.
This figure highlights the case and control sites selected by the spatial random sampling approach.
See this image and copyright information in PMC

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