Other possible mechanisms have been reviewed by Shariq-Usman et al., which include low production of pro-inflammatory cytokines, local vasodilatation, low expression of ACE2, and high production of nitric oxide; however, the authors recommend that this information should be taken with caution since several biases and knowledge gaps were identified (45), and it was demonstrated that smokers have a worst diseases prognosis at the time of infection (46, 47). Here, ACE2 is linked to infection.