Concentrations of nitrogen compounds are related to severe rhinovirus infection in infants. A time-series analysis from the reference area of a pediatric university hospital in Barcelona

Background: There is scarce information focused on the effect of weather conditions and air pollution on specific acute viral respiratory infections, such as rhinovirus (RV), with a wide clinical spectrum of severity. Objective: The aim of this study was to analyze the association between episodes of severe respiratory tract infection by RV and air pollutant concentrations (NO_x and SO₂) in the reference area of a pediatric university hospital. Methods: An analysis of temporal series of daily values of NO_x and SO₂, weather variables, circulating pollen and mold spores, and daily number of admissions in the pediatric intensive care unit (PICU) with severe respiratory RV infection (RVi) in children between 6 months and 18 years was performed. Lagged variables for 0–5 days were considered. The study spanned from 2010 to 2018. Patients with comorbidities were excluded. Results: One hundred and fifty patients were admitted to the PICU. Median age was 19 months old (interquartile range [IQR]: 11–47). No relationship between RV-PICU admissions and temperature, relative humidity, cumulative rainfall, or wind speed was found. Several logistic regression models with one pollutant and two pollutants were constructed but the best model was that which included average daily NO_x concentrations. Average daily NO_x concentrations were related with the presence of PICU admissions 3 days later (odds ratio per IQR-unit increase: 1.64, 95% confidence interval: 1.20–2.25)). Conclusions: This study has shown a positive correlation between NO_x concentrations at Lag 3 and children's PICU admissions with severe RV respiratory infection. Air pollutant data should be taken into consideration when we try to understand the severity of RVis.