When should a diagnosis of influenza be considered in adults requiring intensive care unit admission? Results of population-based active surveillance in Toronto

Table 4 Proportion of subjects with influenza in different populations of screened patients requiring admission to ICUs^a

Influenza season	Age	Admission diagnosis	Admission temperature	Timing during season	Proportion with influenza (95% CI)	Proportion of total influenza cases	Proportion of patients screened
2007/2008 and 2008/2009	Any	Respiratory infection^b or respiratory failure^c	≥38°C	Peak weeks	0.27 (0.15 to 0.43)	0.124	0.020
			<38°C	Peak weeks	0.17 (0.11 to 0.24)	0.268	0.071
			≥38°C	Early or late weeks	0.12 (0.04 to 0.26)	0.052	0.019
			<38°C	Early or late weeks	0.05 (0.03 to 0.08)	0.134	0.124
2009/2010 H1N1 pandemic	Any	Respiratory infection^b	≥38°C	Any time	0.70 (0.35 to 0.93)	0.241	0.041
			<38°C	Any time	0.26; 0.13 to 0.42)	0.345	0.159

^aOR: odds ratio; 95% CI: 95% confidence interval; ^b'pneumonia' and 'other respiratory infection'; ^cincludes 'chronic obstructive pulmonary disease exacerbation', 'asthma exacerbation' and 'respiratory failure'.

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