Table 2.

Number of Fatal Cases and Case-Fatality Proportion of Influenza A and Influenza B Virus-Associated Encephalopathy Cases, by Age Group in Japan, 2010–2015

	Influenza A and Influenza B			Influenza A		Influenza B		P Value
	Fatal /Total	CFPa	P Value	Fatal /Total	CFP	Fatal /Total	CFP
Children (age in years)	22/283	8	–	17/206	8	5/77	7	.62 b
<2	3/33	9c		2/26	8	1/7	14
2–4	6/81	7c		5/63	8	1/18	6
5–12	10/146	7c		8/103	8	2/43	5
13–17	3/23	13c		2/14	14	1/9	11
Adults	14/102	14	.08 d	9/84	11	5/18	28	.07 b,e
18–49	3/41f	7c,g		2/34	6	1/7	14
50–64	3/21	14c,g		3/18	17	0/3	0
≥65	8/40	20c		4/32	13	4/8	50

Abbreviation: CFP, case-fatality proportion.

^aCFP was defined as death at the time of report per number of reported influenza-associated encephalopathy (IAE) cases.

^bComparison of the proportion of influenza A and B virus infections among pediatric and adult IAE cases.

^cCFP was not significantly different among age groups for pediatric (P = .76) or adult IAE cases (P = .25).

^dComparison of the proportion of fatal IAE cases between pediatric and adult age groups.

^eFisher exact test.

^fAll 3 patients who died among those aged 18–49 years were aged 40–49 years.

^gCFP in patients aged 40–64 years was 17% (6/35).