OBJECTIVETo investigate the clinical epidemiologic characteristics and analyze risk factors for acute respiratory syncytial virus (RSV) infection in hospitalized infants with acute lower respiratory tract infection (ALRI).

METHODALRI infants admitted to Children's Hospital of Fudan University from March 1st, 2011 to February 29th, 2012, were enrolled in this study. Patient information included demographic characteristics, feeding history, family status, clinical presentation, accessory examination, treatment and prognosis. According to the etiology of ALRI infants, we compared the seasonal distribution, demographic characteristics, household characteristics and underlying diseases between RSV-positive patients and RSV-negative patients. Univariate and multiple Logistic regression analyses were used to determine factors that were associated with risk of RSV infection.

RESULTAmong 1 726 ALRI infants, there were 913 RSV-positive infants (52.9%). The occurrence of RSV infection had a seasonal variation, with a peak in winter (59.1%). The median (P25, P75) age of RSV infants was 64 (21-155) days. The gestational age (GA) and body weight (BW) was (37.5 ± 2.4) weeks and (3.07 ± 0.66) kg, respectively. The male/female ratio among these was 1.9: 1. RSV infection was more popular among infants in the families with smoking members, crowded living conditions, history of atopic mother. Differences of the proportion of patients with underlying disease between RSV-positive and negative groups were statistically significant (59.4% vs. 54.2%, P < 0.05). Univariate logistic regression demonstrated that factors increasing the risk of RSV infection were: GA<37 weeks (OR = 1.346, 95%CI: 1.037-1.748), birth weight <2 500 g (OR = 1.447, 95%CI: 1.103-1.898), underlying diseases (OR = 1.232, 95%CI: 1.018-1.492), underlying CHD (OR = 1.391, 95%CI: 1.120-1.728), environmental tobacco smoke exposure (OR = 1.254, 95%CI: 1.035-1.519), mother with atopic diseases (OR = 1.827, 95%CI: 1.296-2.573), crowded house with four or more than four family members (OR = 1.232, 95%CI: 1.013-1.498), autumn or winter infection (OR = 1.351, 95%CI: 1.024-1.783; OR = 1.713, 95%CI: 1.332-2.204). Multivariate logistic regression determined the factors increasing the risk of RSV infection were: underlying CHD (OR = 1.298, 95%CI: 1.002-1.681), mother with atopic diseases (OR = 1.766, 95%CI: 1.237-2.520), autumn or winter infection (OR = 1.481, 95%CI: 1.105-1.985; OR = 1.766, 95%CI: 1.358-2.296).

CONCLUSIONThe prevalence of RSV infection was the highest in winter, while preterm and low birth weight infants were more susceptible. Underlying diseases were found in 59.4% cases, CHD was the most common one. The factors increasing the risk of RSV infection were: CHD, mother with atopic diseases, autumn or winter infections.