Table 1.

Distribution of the wind speed, percentage of open landscape, animal densities (cattle and sheep) and temperature according to the cluster variable

Cluster	No. of herds	Wind speed (m/s)	% of open landscape	Cattle density (cows/km2)	Sheep density (sheep/km2)	Temperature (°C)
		(Q1, median, Q3)	(Q1, median, Q3)	(Q1, median, Q3)	(Q1, median, Q3)	(Q1, median, Q3)
1	301	0·6, 0·7, 0·9	0·2, 0·3, 0·4	1·0, 2·9, 4·6	0·2, 0·6, 1·3	3·3, 4·1, 4·9
2	1001	1·2, 1·5, 1·7	0·3, 0·4, 0·6	4·5, 7·5, 11·0	1·3, 2·5, 3·8	7·4, 7·7, 8·2
3	236	1·4, 2·1, 2·8	0·6, 0·8, 0·9	17·3, 30·2, 35·4	5·1, 7·7, 9·5	7·9, 8·4, 8·8

The three clusters resulted from a hierarchical clustering that was performed on the principal component analysis using the five variables. In all, 1537 Swedish dairy herds tested in 2008–2009 were included in this study on risk factors for Coxiella burnetii infection.