Simultaneous circulation of COVID-19 and flu in Italy: Potential combined effects on the risk of death?

Based on data updated to 20 May 2020, the total recorded number of patients who died due to COVID-19-related reasons in Italy was 31,851. Demographic and clinical characteristics of patients who have died (including the number of comorbidities) are extremely relevant, especially to define those with a higher risk of mortality. Health authorities recommend influenza (flu) vaccinations in a number of categories at risk of serious medical complications, including: people aged ≥65 years, or patients with diabetes, cardiovascular diseases, chronic obstructive pulmonary disease (COPD), renal failure, cancer, immunodeficiencies, chronic hepatopathies, and chronic inflammatory bowel diseases. The seasonal flu peak certainly preceded that of the pandemic; however, it would seem clear that the two viruses have been simultaneously circulating in Italy for a while. Hence, after the peak of seasonal flu, influenza-like illness-related (ILI) deaths started to grow again. While some of the excess mortality reported in the ILI group may be attributable to COVID-19, a question arises: do we have to consider this observation as a result of a random sequence of events or a potential relationship between the two viruses play a role? A cooperation mechanism intended at establishing an absolute advantage over the host could also be assumed; this system often takes place to boost the reproductive probabilities. A characterization of those who died due to virus-related reasons can be performed by cross-linking data (stored in different warehouses) from the same geographical area and developing electronic health records. It would be of great relevance to identify people at very high risk of mortality as a result of an overlapping or combination of risk factors that were separately reported in patients who died from COVID-19 or influenza. A description of the subgroup of people at higher risk of mortality will be crucial for prioritizing and implementing future public health prevention and treatment programs.