Table 3.

 Underlying medical conditions among severe cases with confirmed or probable diagnoses of influenza A (H1N1) 2009 virus infection in Japan

Medical condition	Aged <18 years with influenza‐associated encephalopathy	Other cases aged <18 years*	Those aged 18–64 years	Those aged 65 years and older
	n = 48 (with 3 deaths)	n = 38 (with 1 death)	n = 23 (with 8 deaths)	n = 11 (with 11 deaths)
	Total (deaths)	Total (deaths)	Total (deaths)	Total (deaths)
Any one condition	8 (1)	19 (1)	19 (6)	11 (11)
Chronic cardiovascular disease*	0 (0)	0 (0)	2 (2)	2 (2)
Chronic renal disease	0 (0)	0 (0)	3 (1)	1 (1)
Chronic respiratory disease†	5 (0)	17 (1)	4 (1)	4 (4)
Diabetes	0 (0)	0 (0)	3 (1)	3 (3)
Hypertension	0 (0)	0 (0)	4 (2)	2 (2)
Malignant neoplasm	0 (0)	0 (0)	1 (0)	4 (4)
Mental retardation or psychiatric disorder‡	0 (0)	0 (0)	6 (2)	1 (1)
Neurological disease§	1 (0)	0 (0)	1 (0)	1 (1)
Obesity	0 (0)	0 (0)	1 (1)	0 (0)

*Any documented cardiovascular disease except for hypertension.

^†Patients with asthma, emphysema or chronic bronchitis. Among 22 patients under 18 years of age, 21 had asthma. Among eight patients aged 18 years and older, four had chronic obstructive pulmonary disease (COPD; e.g., chronic bronchitis or emphysema), 1 had both asthma and COPD and 3 had asthma only.

^‡Any documented mental retardation or psychiatric disorder, the causes of which included cerebral palsy, Down’s syndrome, epilepsy and schizophrenia.

^§Any documented cerebrovascular disease or congenital anomaly in the central nervous system.