Risk of Developing Asthma After Lower Respiratory Tract Infections with Respiratory Syncytial Virus During Childhood

Background: Recent studies indicate causal relationship between infection by respiratory syncytial virus (RSV) and bronchial asthma. We evaluated the incidence of bronchial asthma in children with RSV positive infection early in their childhood in a nation-wide cohort study. Methods: Children (aged between one month and 15 years) were evaluated for the presence of RSV infection when they presented with one or more acute respiratory tract infection symptoms (fever, cough, cold and wheezing) in a major tertiary care hospital in the Kingdom of Bahrain during a period of seven years. RSV detection was done using nasopharyngeal secretion (NPS) samples by direct antigen detection immunofluorescence technique. Number of children who were later diagnosed with asthma was recorded. Serum IgE levels were estimated. Risk of developing bronchial asthma is represented using relative risk (RR) [95% CI]. Children with asthma without prior RSV infection from the same population formed the historical control. Results: A total of 3782 children diagnosed with respiratory tract infection were recruited. We observed that RSV infection at younger age (during infancy) and severe infection were significantly associated with asthmatic episodes RR [95% CI]: 7 [5.5, 8.2]. Additionally, asthmatics with prior RSV infection had significantly higher total IgE levels (167 ± 37 IU/ml) compared to those without RSV infection (92 ±17 IU/ml). Mean (SD) age of children developing asthma with prior RSV infection was 0.7 (0.42) years compared to the historical control [6.8 (3.8) years] and was statistically significant. Conclusion: Infants with RSV infection have an increased risk of developing bronchial asthma later in the childhood. The more severe the RSV infection, the greater is the severity of bronchial asthma as indicted by serum IgE levels. Asthma in children with RSV infection occurs at much younger age compared to those without RSV infection.