Respiratory virus infections are strongly associated with asthma exacerbations in children and adolescents. In this study, air pollution is not a major factor for ER visits due to asthma exacerbations. Even though the prevalence of respiratory viruses is decreasing, ED visits due to worsening asthma are trending in the fall. This phenomenon may indicate that asthma has worsened due to other causes such as pollen or fluctuations in temperature and air pressure.