LAUSR

The current second wave of the COVID-19 pandemic in Europe constitutes a public health emergency [1], and the purposes of microbiological and biomolecular tests for the identification of SARS-CoV-2 have changed over the last months. For the latter, the number of daily tests performed has drastically increased following the first wave of the pandemic, and it appears clear that daily incidence, as a fraction of tests performed, is substantially different than before testing capacity increased to its current level. Indeed, the current daily incidence’s denominator encompasses not only critical patients with severe symptoms, as during the first wave, but also those subjects who have taken microbiological and biomolecular tests for screening purposes, as a part of contact tracing, or before planned hospital admission, or as a continuous screening tool for health employers. Therefore, making direct comparisons with the COVID-19 epidemiology observed during the first wave of the pandemic is virtually impossible or at least incorrect. The daily absolute numbers of new infected patients provide an epidemiological picture in a specific geographic area but are not so useful in understanding or making predictions about the spread of infection. It appears more appropriate to consider the dynamic of the infection over a short period of time. The trend of daily absolute numbers must be confirmed over a short period of time since an isolated peak of cases could be due to different confounders such as the number of tests performed the day before or might be causal. Moreover, daily data reports have an associated intrinsic delay, since they represent the outcome of the contagion or restrictive measures that have occurred or been adopted up to 14 days before. Similarly, the daily number of patients admitted to the intensive care unit (ICU) should be cautiously interpreted since some patients have deteriorated after symptoms onset and were not immediately admitted to ICU, so a delay also in the trend of these admissions should be considered. The purpose of daily data should be to plan the adoption of contrasting measures to avoid overburdening health-care systems in a short-term period. Unfortunately, when incidence reaches a certain level, failure of contact tracing system seems inevitable since most national health-care systems are not able to manage a larger volume of daily infections. At the population level, it remains fundamental that health-care systems and governments reinforce the concept that there is no significant difference between the viral loads among symptomatic and asymptomatic patients. Therefore, the pivotal role of often undetected asymptomatic subjects in the spread of infection, which is still likely to be underestimated in daily incidence, should be considered. Inevitably, these data distortions have direct implications in the spread of infection [2–4]. Daily data on the COVID-19 pandemic must be carefully disseminated providing an adequate explanation of the meaning and limitations of these results at any levels. Moreover, misinterpretation and incorrect comparisons with past data must be avoided since they can significantly influence public opinion of the current wave’s severity and may induce careless attitudes which are known to increase COVID-19 diffusion.