Starting a few months ago, the coronavirus disease-2019 (COVID-19) has become pandemic and already resulted in more than 25 million confirmed cases worldwide, including over 850,000 associated deaths (https://covid19. who. int/). Older age, hypertension, chronic obstructive pulmonary disease, diabetes and cardiovascular disease are the main risk factors presented for severity and mortality in COVID-19 [1, 2]. Patients with severe COVID-19 infection requiring intensive care may also be challenged to battle against other coexisting infectious agents, such as other respiratory viruses (eg influenza), gram-positive and gram-negative bacteria and fungi (both yeasts and filamentous fungi). As an obvious consequence, secondary infections and/or co-infections in the context of COVID-19 patients are important factors affecting hospitalization time, illness severity and mortality [3, 4]. Corroborating this statement, we have witnessed increasing reports on the co-occurrence of respiratory viruses, like influenza epidemics/pandemics, and secondary invasive fungal infections, resulting in poor patient outcome and, consequently, high mortality rates. Therefore, this critical reality demands an urgency for special focus on different aspects of this new disease [5-7].

It has been established that the activation of antiviral immunity in the host tissue of infected patients (in COVID-19-positive patients, lungs are the main affected organs) can provide a desirable environment for the establishment, growth and development of different classes of microorganisms. For instance, a substantial increase of fungal infections (eg candidiasis, aspergillosis, cryptococcosis, pneumocystosis, histoplasmosis) has been detected in individuals with active infection caused by the human immunodeficiency virus (HIV), severe flu and COVID-19 [6-8].