Analysis of Local Spread of Equine Influenza in the Park Ridge Region of Queensland

In 2007, an incursion of equine influenza (EI) occurred in Australia. Accurate maps of property boundaries were used to examine the pattern and mechanism of local spread of EI. This study focussed on a cluster of infected premises (IPs) at Park Ridge, a peri-urban suburb 26 km south of Brisbane, Queensland. The cluster recorded 437 IPs and 81% of these were not contiguous to a previously IP. The mean distance from each new IP to the closest previous IP was 0.85 +/- 1.50 km with a range of 0.01-12.94 km. Eighty-two percent of new IPs were within 1 km of a previous IP. The spatial mean for each week's new IPs showed a consistent trend of movement from east to west throughout the epizootic consistent with the predominant wind patterns. The findings were consistent with the conclusion that EI will routinely spread over 1-2 km via wind-borne aerosol.