Table 1. Association of physical, chemical, and microbiological water characteristics with Legionella spp. concentration of spa water samples.

Characteristic	No. (%) of positive samples for Legionella		Odds ratios (95% confidence interval)	P
	With characteristics	Without characteristics
Sample Temp≥40 °C	56 (65.1%)	40 (50.6%)	1.820 (0.974–3.402)	0.060
pH≥7.9	65 (55.6%)	31 (64.6%)	0.685 (0.342–1.373)	0.286
Urea ≥0.05 mg/L	17 (37.8%)	69 (75.8%)	0.315 (0.155–0.642)	0.001
Free chlorine ≥0.2 mg/L	4 (13.3%)	92 (68.1%)	0.072 (0.024–0.219)	0.000
Total plate count ≥400 CFU/L	72 (71.3%)	24 (37.5%)	4.138 (2.129–8.044)	0.000
E. coli count ≥3 MPN/L	72 (74.2%)	24 (35.3%)	5.280 (2.691–10.361)	0.000