[Risk factors for influenza A (H1N1)-associated pneumonia on hospitalized people less than 18 years old in China, 2009-2010].
OBJECTIVE
To describe the epidemiological and clinical features of hospitalized people less than 18 years old with influenza A (H1N1)-associated pneumonia and associated risk factors.


METHODS
Through Chinese Reporting System of Influenza A (H1N1), children aged under 18 years who were hospitalized with laboratory confirmed influenza A (H1N1), case report forms and related information on pneumonia were collected between 1 September 2009 and 4 July 2010. Epidemiological and clinical characteristics including demographics, underlying chronic diseases, treatment, complications and clinical outcome etc. were described. Hospitalized children with pneumonia were compared with those without the above mentioned features, through the univariate and multivariate analysis.


RESULTS
There were 4240 influenza A (H1N1)-associated hospitalized children with case report forms identified. Of the 4107 influenza A (H1N1)-associated hospitalized children with related information on pneumonia shown in the case report forms, 2289 (55.7%) of them had pneumonia. Hospitalized children with influenza A (H1N1)-associated pneumonia had a younger median age (4.9 year old), when compared with those without pneumonia (13.1 year old, P<0.0001). When compared with the hospitalized children without pneumonia, those hospitalized children with pneumonia were more likely to require intensive care unit care, using mechanical ventilation equipment to develop ARDS, respiratory failure or leading to death. Data from multivariate analysis showed that children aged<6 months (OR=7.08, 95%CI: 4.15-12.06) between 6 and 23 months (aOR=8.26, 95%CI: 6.10-11.20) or between 2 to 4 year old (aOR=9.53, 95%CI: 7.39-12.29) were more likely to develop pneumonia than children aged 5 to 17. Factors as having asthma (OR=12.19, 95%CI: 5.18-28.72), cardiovascular disease (OR=5.19, 95%CI: 1.94-13.90), chronic renal diseases (OR=2.14, 95%CI: 1.02-4.53), chronic hepatic diseases (OR=5.26, 95%CI: 1.40-19.81) and allergy (OR=2.54, 95%CI: 1.64-3.93) were significantly associated with influenza A (H1N1)-associated pneumonia. Risk of complication with pneumonia had an increase when oseltamivir treatment was initiated>2 days after the onset of illness.


CONCLUSIONS
Pneumonia was a common complication among children hospitalized with influenza A (H1N1). Hospitalized children with influenza A (H1N1)-associated pneumonia were more likely to develop either severe clinical courses or outcomes than those without pneumonia.
Institute of Virus Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China.
Cui-ling
CL
Xu
Fan
F
Yuan
Min
M
Chen
Shan-hua
SH
Sun
Jing-hong
JH
Shi
Li-jie
LJ
Wang
Tao
T
Chen
Jing
J
Yang
Ni-juan
NJ
Xiang
Yan-ping
YP
Zhang
Shi-wen
SW
Wang
Yue-long
YL
Shu
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000150:complications*; D011024:Pneumonia, Viral / Q000209:etiology*; D012307:Risk Factors