1. Introduction
The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is the cause of the COVID-19 pandemic, for which there is currently no specific pharmacotherapy. In the intensive care unit, depending on the severity of the COVID-19 infection, patients might receive supportive care such as oxygen supply, interferons, glucocorticoids, anti-virals, chloroquine, and macrolides given as deemed appropriate. The SARS-CoV-2 infection produces either non-severe or severe symptoms and, in the latter case, it may precipitate into severe acute respiratory syndrome (SARS) and ultimately death [1,2,3,4,5,6,7,8,9]. Aging and different comorbidities are associated with patients’ critical status. Most patients display lymphopaenia and eosinopaenia, and critical ones show extremely low levels of eosinophils, suggesting that eosinopaenia may be a potential diagnostic biomarker [1]. Most serious cases of SARS are closely associated with cardiac dysfunction/injury, respiratory distress/illness, coagulopathy, hypoproteinaemia, acidosis, hypoxia and a cytokine storm mainly involving IL-1β, IL-6, IL-8, IL-10 and TNFα [1,2,3,4,5,6,7,8,9]. For instance, hypertension, an age-related disease, is the most common comorbidity (15–31% up to 24–58% in severe disease cases according to clinical reports), while only five cases of asthma (0.9%) were identified in one report of 548 infected patients in Wuhan [6], but no other asthmatic or allergic patients were described in other reports [1,2,3,4,5,7,8,9], considering that the overall prevalence of asthma is estimated to be 6.4% in Wuhan [6] and ~ 4% in China [10]. Viral infections usually increase the risk of allergic disease exacerbation [1]; however, the reported data seem to suggest that, in this case, the opposite is true. Indeed, in more than 72.000 patient cohorts examined, the number of patients defined as asthmatic was low (5), which suggests that asthmatics might be protected from virus-induced SARS, whereas pre-existing hypertensive disease and/or pre-existing antihypertensive treatments may represent a risk factor for increased virus infection, considering that the overall prevalence of hypertension in Chinese adult population ≥18 years of age is estimated to be ~ 23% [11]. Therefore, according to the clinical picture of infected patients, Th2-mediated allergic diseases (usually with high eosinophil counts) may play a protective role against SARS (usually with low eosinophil counts), while yet unknown mechanisms related to hypertensive conditions may exacerbate symptoms. To complete the picture, COVID-19 hospitalized patients suffering from chronic renal disease were usually low (0-3%) [1,2,3,4,5,6,7,8,9] if compared with the prevalence of the disease in China (10.2-11.3%) [12], suggesting that chronic kidney disease patients might be protected from COVID-19 as for asthma patients.