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

Viral respiratory tract infection, with rhinovirus accounted for two thirds, was found to be associated with greater than 80% of asthma exacerbations in children in studies in the 1990s [14] . However, the prevalence of respiratory viral infection varies greatly across different places; for example, influenza is associated with more hospitalization among children in Hong Kong compared with temperate region [7] . Recent observational studies have shown that influenza infection can be associated with asthma exacerbations. Nevertheless, a metaanalysis failed to support the protective effect of influenza vaccination in asthma exacerbations [3] . Newly discovered respiratory viruses such as human metapneumovirus may also play a role [20] . Triggers other than respiratory tract infection, like air pollutions may become more prevalent over time and supersede respiratory tract infections as a major trigger. Thus, we carried out a prospective study to delineate the current role of different viral respiratory tract infections including newly discovered respiratory viruses in asthma exacerbation in children in our locality.