Table 1. 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.

Variable group	Variable name	Variables (Units)
Meteorological	RAIN t−1,t−2,…,t−5	Rainfall (mm day−1)a
covariates	RH_9AM t−1,t−2,…,t−5	Relative humidity (%) measured daily at 9ama
(time-lagged)	RH_3PM t−1,t−2,…,t−5	Relative humidity (%) measured daily at 3pma
	TEMP_MAX t−1,t−2,…,t−5	Maximum daily air temperature (°C)a
	TEMP_MIN t−1,t−2,…,t−5	Minimum daily air temperature (°C)a
	WIND_SPDundir t−1,t−2,…,t−5	Maximum daily wind speed – undirected (km hour−1)a , b
	WIND_SPDdir(k) t−1,t−2,…,t−5	Maximum daily wind speed – directed (km hour−1)a , b
Premises	AREA	Area (acres)
attributes	HORSE_DENSITY	Horse density (horses acre−1)
	HORSES_NUMBER	Number of horses
	SHARED_FENCE	Length of shared fence with other horse premises (m)
	VACC	Vaccination status (1 = Yes, 0 = No)a
	VACC_DAYS	Days since vaccinationa
Spatial	ELEV	Elevation (m)
covariates	HUMAN_DENS	Human population density within approximately 1 km of the premises (people km−2)
	ROAD_DIST	Distance to nearest main road (km)c

^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).