Relationship between lower respiratory tract infections caused by respiratory syncytial virus and subsequent development of asthma in Japanese children.

Several studies in Western countries have found that lower respiratory tract infections (LRTIs) caused by the respiratory syncytial virus (RSV) in infancy may subsequently trigger the development of asthma. In this study, we enrolled 262 infants under the age of 3 who had been admitted to our hospital with LRTI between September 2002 and August 2003. RSV infection was diagnosed in these patients using an RSV rapid diagnostic kit and by measuring antibody titers in paired serum samples. In March 2009, we sent questionnaires on post-discharge allergic conditions to the families of the 249 patients, excluding 13 who had a prior history of asthma. A total of 133 responses were received (response rate, 53.4%); RSV was detected in 36 patients of the RSV group and 97 patients of the non-RSV group. Wheezing was experienced post-discharge by 10 patients in the RSV group (27.8%) and 32 in the non-RSV group (33.0%) (P = 0.57). Four patients in the RSV group (11.1%) and 6 in the non-RSV group (6.2%) (P = 0.34) were treated for asthma. This study revealed that RSV LRTI in infancy does not predispose children to subsequent development of asthma at the age of 7 years and 7 months. We believe that this is the first Japanese survey that has examined the relationship between RSV LRTI in infancy and the subsequent development of asthma.