This paper presents the results of spatio–temporal analyses and epidemic modelling of
HPAI H5N1 outbreaks that occurred in four provinces of the Mekong River Delta, Vietnam between January and March 2009. Significant spatio–temporal interaction of disease risk was observed within a distance of 10 km and 12 days following the detected onset of clinical signs. We estimate that the household-to-household infection rate within a commune was approximately 50 times greater than the household-to-household infection rate between communes. Our findings show that the predominant mechanism of infection transfer was local spread. A comparison of disease control procedures and veterinary capacity in communes with relatively high and low infection rates should help to identify procedures essential for effective outbreak management in this area of Vietnam.