Table 2. Univariate associations of STEC O91 of sequence type 442 with severe disease by use of exact logistic regression*.

Severe disease	ST442, no. (%)	Non-ST442, no. (%)	Odds ratio	95% Confidence interval	p value
HUS	4 (20)	0 (0)	27.8†	3.29–∞	<0.01
BD	3 (15)	5 (6)	3.4	0.47–20.1	0.25
HUS or BD	7 (35)	5 (6)	7.8	1.83–36.6	<0.01

*Reference group consisted of persons who had nonbloody diarrhea or who were asymptomatic carriers. STEC, Shiga toxin-producing Escherichia coli; ST, sequence type; HUS, hemolytic uremic syndrome; BD, bloody diarrhea.
†Mean unbiased estimate.