Clinical features of children infected with influenza virus A in year 2009 in Wuhan area

Abstract

Objective To explore the clinical and pandemic features and respiratory pathogen co-infection characteristics of children infected with influenza virus A(Flu A)in year 2009. Methods A retrospective study of hospitalized children with flu-like clinical symptoms in 2009 was conducted.The peripheral blood serum was analyzed to detect common respiratory agents, including Flu A, respiratory syncytial virus, adenovirus, influenza virus B, parainfluenza virus 1, 2 and 3, chlamydia pneumonia and mycoplasma pneumonia, klebsiella pneumonia(KP), haemophilus in-fluenza and legionella pneumophila by using indirect immunofluorescence test for the antibody detection (IgM). And a standard medical history was recorded, including epidemiological data, clinical manifestation, and the length of hospital stay, white blood count and chest X-ray elsewhere.All specimens were collected in Department of Pediatrics, Zhongnan Hospital of Wuhan University, from Jan.2009 to Dec.2009. Results Flu A was detected in 234 of the 599 (39.1%, 234/599 cases) flu-like children.The mean age was 48.8 months (range from 3 to 167 months). The detection rate in less than 1-year-old group (11.1%, 18/162 cases) was obviously lower than that of the older groups(P<0.001). Especially for the group< 6 months, there was only 1 infant (1.43%, 1/70 cases) with Flu A positive.Compared with Flu A negative group, the main clinical features of children with Flu A positive group were fever(78.2%, 183/234 cases, P=0.013) and cough(76.5%, 179/234 cases, P=0.04), however asthma (14.1%, 33/234 cases, P=0.003) and diarrhea (6.0%, 14/234 cases, P=0.001) cases were less.The detection rates of Flu A reached a peak of 57.0% in November and December, and a secondary peak of 45.0% in May and June.Flu A infection children less than 1 year old were simple in etiology.The children were older, the etiology was more complex.The primary coinfection pathogen was KP (53.8%, 126/234 cases) and Flu B(48.3%, 113/234 cases). Compared Flu A coinfection with or without KP, there was no difference between these 2 groups in the clinical features. Conclusions Influenza A is the main pathogen of hospitalized children with flu-like symptoms in 2009.Children over 1 year old age were the major infection groups of Flu A. The detection rates of Flu A reached peaks in May to June and November to December.Flu A positive children were prone to KP coinfection. Key words: Influenza A; Child; Respiratory tract infection; Coinfection