Explanatory variables analysed for associations with time to infection of premises in the largest cluster, northwest of Sydney, during the 2007 equine influenza outbreak in Australia.

aTime-changing covariate.bMaximum daily wind speed was either based on wind from all directions (‘undirected’) or wind only from within 45° arcs centred on the direction of the k nearest infected premises for k = 1,2,3 (see Figure 2 for details) assuming that premises were infectious for 14 days and one of the nearest k infective premises was the source of infection.cMain roads include freeways, highways, primary and arterial roads (Classes 1–3).