Unveiling the Risk Period for Death After Respiratory Syncytial Virus Illness in Young Children Using a Self-Controlled Case Series Design

Background Respiratory syncytial virus (RSV)–related acute lower respiratory infection is an important cause of death in infants and young children. However, little is known about the risk period for RSV-related deaths after presentation to health services with an RSV illness. Methods Using the Scottish national mortality database, we identified deaths from respiratory/circulatory causes (hereafter “respiratory/circulatory deaths”) in young children aged Results We included 162 respiratory/circulatory deaths, of which 36 occurred in children with a history of laboratory-confirmed RSV infection. We found that the mortality risk decreased with time after the RSV episode and that the risk was statistically significant for the month after RSV illness. More than 90% of respiratory/circulatory deaths occurring within 1 week after the RSV episode were attributable to RSV (attributable fraction, 93.9%; 95% confidence interval, 77.6%–98.4%), compared with about 80% of those occurring 1 week to 1 month after RSV illness (80.3%; 28.5%–94.6%). Conclusions We found an increased risk of death in the first month after an RSV illness episode leading to healthcare attendance. This provides a practical cutoff time window for community-based surveillance studies estimating RSV-related mortality risk. Further studies are warranted to assess the mortality risk beyond the first month after RSV illness episode.