Background: In response to the coronavirus disease (COVID-19) outbreak that unfolded across Europe in 2020, the World Health Organisation called for repurposing existing influenza surveillance systems to monitor COVID-19. This analysis aimed to compare descriptively the extent to which influenza surveillance systems were adapted and enhanced, and how COVID-19 surveillance could ultimately benefit or disrupt routine influenza surveillance. Methods: We used a previously developed framework in France, Germany, Italy, Spain and the United Kingdom to describe COVID-19 surveillance and its impact on influenza surveillance. The framework divides surveillance systems into 7 sub-systems and 20 comparable outcomes of interest, and uses 5 evaluation criteria based on WHO guidance. Information on influenza and COVID-19 surveillance systems were collected from publicly available resources shared by European and national public health agencies. Results: Overall, non-medically attended, virological, primary care and mortality surveillance were adapted in most countries to monitor COVID-19, whilst community, outbreak, and hospital surveillance were reinforced in all countries. Data granularity improved, with more detailed demographic and medical information recorded. A shift to systematic notification for cases and deaths enhanced both geographic and population representativeness whilst the sampling strategy benefited from the roll out of widespread molecular testing. Data communication was greatly enhanced, contributing to improved public awareness. Conclusions: Well-established influenza surveillance systems are a key component of pandemic preparedness and their upgrade allowed European countries to respond to the COVID-19 pandemic. However, uncertainties remain on how both influenza and COVID-19 surveillance can be jointly and durably implemented.

INTRODUCTION. Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract illness in young children and can also cause influenza-like illness (ILI). Here we investigated the epidemiological features of RSV infection in pediatric ILI cases in Lombardy (a region in Northern Italy accounting nearly 10-million inhabitants) from 2014-2015 to 2020-2021 winter seasons. MATERIAL AND METHODS. Data for this study were retrieved and statistically analyzed from the database of virological influenza surveillance of the regional reference laboratory for Lombardy within the Italian influenza surveillance network (InfluNet). RESULTS. RSV accounting for nearly 19% of pediatric ILI with a risk of infection nearly 2-fold greater than that of individuals ≥15 years. The RSV positivity rate increased to 28% considering 0-5 years old children. Although in children ≤5 years the risk of infection from influenza viruses resulted nearly 2-fold higher than the risk of RSV infection, the age group 4-6 months and 7-12 months showed 5-fold greater risk of infection from RSV than from influenza. Children ≤5 years of age with presence of one or more comorbidities had a nearly 5-fold greater risk of getting RSV infection than otherwise healthy 0-5 years old children. DISCUSSION. The use of the ILI sentinel surveillance allowed us to identify groups at higher risk of RSV and influenza infection and to define the start, duration, timing and intensity of the RSV and influenza community circulation, determining thresholds based on historical data. This surveillance approach can be implemented to assess the nearly real-time RSV circulation and impact.