Table 3.

Estimated Case Fatality Ratio among Medically Attended Cases

Period	Age	Viral Subtype	N (Outpatient)	N (Inpatient)	P (H|ILI)	P (D|H)	Case Fatality Ratio/% (95% Confidence Interval)
Pandemic (2009–2011)	All ages	pH1N1	541	358	0.052	0.087	0.45 (0.23, 0.67)
		H3N2	273	31	0.004	0.065	*
		B	33	12	0.061	0.000	*
		Negative	971	117	0.031	0.043	0.13 (0.01, 0.25)
	18–64	pH1N1	539	313	0.052	0.083	0.43 (0.21, 0.65)
		H3N2	254	14	0.000	0.000	*
		B	31	8	0.065	0.000	*
		Negative	924	84	0.025	0.024	*
	65+	pH1N1	2	45	0.000	0.111	*
		H3N2	19	17	0.053	0.118	*
		B	2	4	0.000	0.000	*
		Negative	47	33	0.149	0.091	*
Post-pandemic (2012–2015)	All ages	pH1N1	667	218	0.019	0.046	0.09 (0.02, 0.16)
		H3N2	1345	424	0.009	0.047	0.04 (0.01, 0.07)
		B	639	185	0.020	0.070	0.14 (0.04, 0.25)
		Negative	4089	422	0.018	0.107	0.19 (0.12, 0.26)
	18–64	pH1N1	639	174	0.019	0.046	0.09 (0.01, 0.16)
		H3N2	1248	191	0.006	0.016	0.01 (0.00, 0.02)
		B	602	118	0.017	0.042	0.07 (0.00, 0.14)
		Negative	3778	244	0.016	0.057	0.09 (0.04, 0.14)
	65+	pH1N1	28	44	0.036	0.045	*
		H3N2	97	233	0.041	0.073	*
		B	37	67	0.081	0.119	*
		Negative	311	178	0.039	0.174	0.67 (0.24, 1.1)

Data are for the pandemic and post-pandemic periods, computed as the product of the risk of FLU002 influenza-like illness outpatients getting hospitalized and the FLU003 hospitalized patients having died at day 60.

Abbreviations: P (D|H), probability of death given hospitalization; P (H|ILI) , probability of hospitalization given influenza-like illness.

*Case fatality rate not calculated when fewer than 100 outpatients or inpatients contained in any stratum.