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.

A valid measurement of the SARS-CoV-2 incubation period is needed for case definitions and for adapting appropriate isolation measures but is challenging in an emergency context. The objective was to systematically review recent literature of reported estimates of the distribution of incubation period of SARS-CoV-2 for describing the distribution and its variability and dispersion through meta-analysis. A systematic review search was carried out up to July 1st 2020 of all identified references available reporting the SARS-CoV-2 incubation. Individual mean and standard deviation were used to produce the pooled estimate. Heterogeneity was also assessed using I2 statistics and sources of heterogeneity were explored using a meta-regression. The main outcome was the SARS-CoV-2 incubation period defined as the time from exposure to onset of clinical illness. In total, 43 studies were eligible, including 12 (27.9%) cohorts and 31 (72.1%) case reports and series. The pooled estimate of the mean incubation period across the studies was 6.24 days, 95% CI [5.80;6.69] ranging from 2.33 to 17.60 days. Shorter incubation periods were reported in cohorts compared to case series (p<0.01) and among studies with high proportions of males (p<0.05). The mean incubation period will help for identification times of exposure but determinants of its variations/range might be explored for potential links with clinical outcome or early pathogenic steps. The impact of individuals with extreme values of incubation on the outbreak dynamic should be evaluated taking account for the basic reproductive number. A real time of meta-analysis, called the InCoVid Lyon, is proposed.