question: Clinical presentations of COVID-19 exhibit a relative variation that might have roots in various circumstances The initial infectious dose is a decisive factor in determining the fate of some viral and bacterial infections Regarding the importance of inflammation and immunopathogenesis in the progression of COVID-19, the initial infectious dose of severe acute respiratory syndrome coronavirus 2 might have an impact on the initial inflammation and therefore the incubation period of the disease A quick progression to severe disease might decrease the chance for successful therapy Therefore, more release of danger-associated molecular patterns and more cytokine responses are expectable in the case of higher infectious doses Herein we discuss the impact of initial infectious dose in the pathogenesis of similar infections such as MERS and influenza