Understanding the September asthma epidemic

Abstract

The highly predictable increase in emergency department visits, hospital admissions, and unscheduled physician consultations for childhood asthma in North America every September is uniquely related to school return. Rhinovirus infection is likely the major trigger, initially affecting asthma in school-age children, followed by similar but lesser increases in asthma morbidity in younger children and in adults. Low use of asthma medications during summer may fuel the epidemic, which may be attenuated by the short-term addition of an effective controller therapy.

Randomized Trial of Omalizumab (Anti-IgE) for Asthma in Inner-City Children

“…Viral respiratory infections are a major cause of exacerbations, especially in the fall, with the start of school, 24,25 but they were identified in less than 60% of the samples available for analysis, suggesting that other factors, such as allergen exposure, pollution, stress, or bacteria, also contribute to the risk of exacerbation. 25,32 Omalizumab was equally effective in reducing exacerbations in the fall and the spring, with or without a viral infection, but it did not appear to prevent viral respiratory infections, since the rate of virus detection was similar in the omalizumab and placebo groups at a study visit not associated with an exacerbation.…”

Indoor airborne fungi and wheeze in the first year of life among a cohort of infants at risk for asthma

“…Children born in the summer and those with fall mold collection dates, an overlapping group in our study, were at an increased risk of wheeze in unadjusted logistic regression models. These observations could represent exposure to relatively high indoor fungal levels at a young age or exposure to respiratory syncytial virus or rhinovirus at an age when small airway size can be a factor in the development of wheeze during viral infection (Heymann et al, 2004;Sears and Johnston, 2007). Nonetheless, ''high levels'' of Penicillium remained a significant predictor of wheeze even after accounting for the effects of season of mold collection, the age of the baby at the sample collection date and day care attendance, a surrogate measure of respiratory infection during infancy and early childhood (Ball et al, 2000;Stark et al, 2003).…”

Respiratory virus transmission dynamics determine timing of asthma exacerbation peaks: Evidence from a population-level model

“…For children, we find that daily viral prevalence is the strongest predictor of asthma hospitalizations, with transmission reduced by 45% (95% credible interval =41-49%) during school closures. We detect a transient period of nonspecific immunity between infections lasting 19 (17)(18)(19)(20)(21) d. For adults, hospitalizations are more variable, with influenza driving wintertime peaks. Neither particulate matter nor ozone was an important predictor, perhaps because of the large geographic area of the populations.…”

“…In children, this pattern strongly reflects the school calendar (15)(16)(17). A wave of asthma exacerbations in children ensues shortly after the return to school after summer break (shown in Fig.…”

“…1 for Texas in midAugust). The return-to-school peak has been termed the "September epidemic of asthma" (14) and noted in the United Kingdom (18), Canada (17,19), and elsewhere (20). Asthma hospitalizations also seem to rise after the 2-wk winter holiday (late December through early January) and 1-wk spring break (late March) (Fig.…”