Is respiratory viral infection really an important trigger of asthma exacerbations in children?

Lee, So-lun; Chiu, Shui-seng Susan; Malik, Peiris Joseph S.; Chan, Kwok-hung; Wong, Hing-sang Wilfred; Lau, Yu-lung

A community study carried out in Southampton, UK over a decade ago found viral infections in >80% of asthma exacerbations in 9-11-year-old children [14] . Our virus detection rate was only 36.7 % of all unscheduled sick visit in children aged 6 to 14 years old and the rate was not significantly different between asthma exacerbations (34.8 %) and that of other diagnoses (39.2 %). This low detection rate was not due to inadequate power based on a priori sample size calculation. Neither was it due to virus detection method as we included PCR detection of more scores ≤3 that did not warrant unscheduled visits. The recently discovered respiratory viruses including human metapneumonvirus, human coronavirus NL 63, OC43, 229E, HKU1, and bocavirus in addition to the virus detection method adopted in the Southampton study, i.e., using IF detection of viral antigens and culture for five respiratory viruses, viz. influenza viruses types A & B, RSV, parainfluenza virus, and adenovirus and PCR for detection of rhinovirus. Our previous study using PCR method in detecting rhinovirus was shown to be comparable to the global literature [5] . Our result was comparable to a clinic-based prospective study [19] and more closely matched to the Canadian case-control study conducted in September 2001 before the epidemics of severe acute respiratory syndrome (SARS) in which 62% of asthma children attending emergency department for exacerbations had respiratory viruses isolated [13] .