Ambient Particulate Matter and Respiratory Syncytial Virus

Presenter: M. Raes (e-mail: [e-mail])

Introduction: Respiratory syncytial virus (RSV) is the primary pathogen responsible for yearly outbreaks of lower respiratory tract infections in children and is a major cause of hospitalization and mortality in very young infants. Although air pollutants are known to affect lung inflammation and immune responses, only few studies have addressed the triggering effect of ambient air pollution on the occurrence of RSV. In this study, we investigated the short-term association between positive RSV detection tests and exposure to particulate matter with diameter less than 2.5 µm in diameter (PM2.5).

Materials and Methods: We collected data on 11,845 laboratory-confirmed inpatient and ambulatory RSV cases under the age of 3 years from 9 hospitals in Belgium during the epidemic peak months (November to January) of 9 RSV seasons (2005–2014). Daily PM2.5 concentrations at the municipality of the hospital were estimated by a spatial-temporal interpolation model that combines data from monitoring stations with land cover data obtained from satellite images. We used a time-stratified case-crossover design and conditional logistic regression models adjusted for temperature, humidity, and public holidays, and we allowed for a non-linear exposure-response association. Based on the pathogenesis of RSV, we calculated the mean PM2.5 exposure up to 10 days before the RSV detection test (lag 0–10 days), and the mean exposure during smaller time windows (lag 0–1, lag 2–4, lag 5–7, lag 8–10 days, lag 11–13 days).

Conclusion: Fig. 1 represents the relative risk for positive RSV detection estimated for the different exposure windows. For an increase in mean lag 0–10 pm2.5 from 1 µg/m³ (minimum) to 34.9 µg/m3 (90th percentile), the estimated increase in positive RSV tests was 34.3% (95% CI: 4.6–72.4%). Effect estimates of specific exposure windows were largest for lag 5–7 days (17.1%, 95% CI: 2.2–40.2%) and lag 8–10 days (29.0%, 95% CI: 6.1–56.9%), corresponding to the incubation and/or initial infection stages. Alternative statistical methods (symmetric bidirectional case-crossover and quasi-Poisson time-series analyses) gave similar results. Findings from this study suggest that particulate matter air pollution exposure may act as a trigger for the occurrence of RSV symptoms.

Keywords: respiratory syncytial virus, RSV, particulate matter, PM2.5