Prevalence and seasonality of six respiratory viruses during five consecutive epidemic seasons in Belgium

BackgroundAcute Respiratory Infections (ARIs) are a major health problem, especially in young children and the elderly.ObjectivesInsights into the seasonality of respiratory viruses can help us understand when the burden on society is highest and which age groups are most vulnerable.Study designWe monitored six respiratory viruses during five consecutive seasons (2011–2016) in Belgium. Patient specimens (n = 22876), tested for one or more of the following respiratory viruses, were included in this analysis: Influenza viruses (IAV & IBV), Human respiratory syncytial virus (hRSV), Human metapneumovirus (hMPV), Adenovirus (ADV) and Human parainfluenza virus (hPIV). Data were analysed for four age categories: <6y, 6–17y, 18–64y and ≥65y.ResultsChildren <6y had the highest infection rates (39% positive vs. 20% positive adults) and the highest frequency of co-infections. hRSV (28%) and IAV (32%) caused the most common respiratory viral infections and followed, like hMPV, a seasonal pattern with winter peaks. hRSV followed an annual pattern with two peaks: first in young children and ±7 weeks later in elderly. This phenomenon has not been described in literature so far. hPIV and ADV occurred throughout the year with higher rates in winter.ConclusionsChildren <6y are most vulnerable for respiratory viral infections and have a higher risk for co-infections. hRSV and IAV are the most common respiratory infections with peaks during the winter season in Belgium.