Transmission of the Highly Pathogenic Avian Influenza Virus H5N1 within Flocks during the 2004 Epidemic in Thailand
1Department of Livestock Development, Ministry of Agriculture and Cooperatives, 2Food and Agriculture Organization of the United Nations, Regional Office for Asia and the Pacific, 3National Institute of Animal Health, Bangkok, and 4Faculty of Veterinary Medicine, Kasetsart University, Nakhon Pathom, Thailand; 5Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
This present study is the first to quantify the transmission of avian influenza virus H5N1 within flocks during the 2004 epidemic in Thailand. It uses the flock‐level mortality data to estimate the transmission‐rate parameter (β) and the basic reproduction number (R0). The point estimates of β varied from 2.26/day (95% confidence interval [CI], 2.01–2.55) for a 1‐day infectious period to 0.66/day (95% CI, 0.50–0.87) for a 4‐day infectious period, whereas the accompanying R0 varied from 2.26 (95% CI, 2.01–2.55) to 2.64 (95% CI, 2.02–3.47). Although the point estimates of β of backyard chickens and fighting cocks raised together were lower than those of laying hens and broiler chickens, this difference was not statistically significant. These results will enable us to assess the control measures in simulation studies. They also indicate that, for the elimination of the virus, a critical proportion of the susceptible poultry population in a flock (i.e., 80% of the population) needs to be vaccinated.
Received 19 December 2006; accepted 9 February 2007; electronically published 25 October 2007.
Cited by
Online publication date: 30-Apr-2009.
CrossRef
Online publication date: 1-Mar-2009.
CrossRef
Online publication date: 1-Feb-2008.
CrossRef
-
Potential conflicts of interest: none reported.
Financial support: Royal Government of Thailand (scholarship to T.T.); Thai Department of Livestock Development, Ministry of Agriculture and Cooperatives (support to T.T.).





