Risk factors and characteristics of H5N1 highly pathogenic avian influenza (HPAI) post-vaccination outbreaks

Henning, Joerg, Pfeiffer, Dirk and Vu, Le (2009) Risk factors and characteristics of H5N1 highly pathogenic avian influenza (HPAI) post-vaccination outbreaks. Veterinary Research, 40 3: 1-12. doi:10.1051/vetres:2008053

Author Henning, Joerg
Pfeiffer, Dirk
Vu, Le
Title Risk factors and characteristics of H5N1 highly pathogenic avian influenza (HPAI) post-vaccination outbreaks
Journal name Veterinary Research   Check publisher's open access policy
ISSN 0928-4249
Publication date 2009-05-01
Year available 2008
Sub-type Article (original research)
DOI 10.1051/vetres:2008053
Open Access Status DOI
Volume 40
Issue 3
Start page 1
End page 12
Total pages 12
Editor J. Charley Poulain
J. M. Aynaud
Place of publication Paris, France
Publisher EDP Sciences
Language eng
Subject 070704 Veterinary Epidemiology
Abstract Highly pathogenic avian influenza (HPAI) virus H5N1 is now endemic in South-East Asia but HPAI control methods differ between countries. A widespread HPAI vaccination campaign that started at the end of 2005 in Viet Nam resulted in the cessation of poultry and human cases, but in 2006/2007 severe HPAI outbreaks re-emerged. In this study we investigated the pattern of this first post-vaccination epidemic in southern Viet Nam identifying a spatio-temporal cluster of outbreak occurrence and estimating spatially smoothed incidence rates of HPAI. Spatial risk factors associated with HPAI occurrence were identified. Medium-level poultry density resulted in an increased outbreak risk (Odds ratio (OR) = 5.4, 95% confidence interval (CI): 1.6–18.9) but also climatevegetation factors played an important role: medium-level normalised difference vegetation indices during the rainy season from May to October were associated with higher risk of HPAI outbreaks (OR = 3.7, 95% CI: 1.7–8.1), probably because temporal flooding might have provided suitable conditions for the re-emergence of HPAI by expanding the virus distribution in the environment and by enlarging areas of possible contacts between domestic waterfowl and wild birds. On the other hand, several agricultural production factors, such as sweet potatoes yield, increased buffalo density, as well as increased electricity supply were associated with decreased risk of HPAI outbreaks. This illustrates that preventive control measures for HPAI should include a promotion of low-risk agricultural management practices as well as improvement of the infrastructure in village households. Improved HPAI vaccination efforts and coverage should focus on medium poultry density areas and on the pre-monsoon time period.
Keyword Avian influenza
Risk factor
HPAI outbreak
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Article 15, pdf 1-12.

Document type: Journal Article
Sub-type: Article (original research)
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Created: Thu, 03 Sep 2009, 18:19:38 EST by Mr Andrew Martlew on behalf of School of Veterinary Science