LAUSR

Dear Editor, During the last months, the COVID-19 pandemic revealed the dramatic impact that respiratory viruses can generate on the overall population, with considerable consequences on social dynamics and health-care systems. Although it is generally less severely disrupting, influenza epidemic can nonetheless affect public health, communities, and economies worldwide. In fact, previous estimates indicated that almost 300,000–650,000 deaths occur annually worldwide due to seasonal influenza viruses [1], contributing to a substantial annual burden of deaths globally. Influenza is a highly contagious respiratory tract infection that affects millions of adults each year; recently, people suffering from obesity have been included in the high-risk population for seasonal influenza, together with children, elderly, and immunocompromised people [2]. The association between excess adiposity and pulmonary comorbidities has long been widely acknowledged, but the role of obesity as a risk factor for infectious diseases has been highlighted much more recently only [3, 4]. Obesity is indeed characterized by an altered metabolic milieu, resulting in hormone dysregulation, derailment of the immune response, and creation of a pro-inflammatory environment, which can easily promote infections [5, 6]. The literature suggests that obesity delays the clearance of influenza viral load and prolongs shedding duration, resulting in long-term transmission and delayed recovery [7]. In actual fact, adults suffering from overweight and obesity, compared with normal-weight subjects, show higher risk of hospitalization for respiratory illness during seasonal influenza and, furthermore, of prolonged hospital stay [8]. Indeed, during the 2009 influenza pandemic, obesity was recognized as an independent risk factor for severe H1N1 pulmonary infection [9], as well as for the development of influenza-related systemic complications and for increased morbidity and mortality resulting from infection [10]. Moreover, as recently reported, obesity impairs vaccine response to several infectious diseases, affecting, in the case of influenza, the most efficient primary prevention [11]. It is therefore conceivable that, because of its favorable effects on weight loss, obesity-related comorbidities and on overall pulmonary function, bariatric surgery (BS) can contribute to reducing the incidence and improving the clinical course of influenza in patients suffering from obesity. We investigated the impact of BS on influenza, by comparing the clinical course of influenza-like illness (ILI) in patients who had undergone BS to that in adult with obesity candidates for a bariatric procedure in a retrospective observational study involving 2 major centers of BS in Italy and France. Data regarding patients that had undergone a bariatric procedure were compared with those of subjects with obesity waiting for surgery in the above-mentioned hospitals. All the subjects completed a web-based questionnaire (Google ® FORMS). Clinical expression of influenza virus infection was assessed by measuring illness-related symptoms and outcome parameters, including sick leaves. From the analysis, we * Federico Marchesi [email protected]