ACE2 and COVID-19: Overall, these studies offer several hypotheses as to how viral mechanisms could lead to smell loss in COVID-19 patients: one ACE2 mechanisms in olfactory neurons lead to a direct modulation of olfactory sensitivities or even cell death; two ACE2 mechanisms in non-neural olfactory cells lead to indirect modulation of OSN function and; three ACE2 mechanisms in neighboring glial cells lead to increased inflammatory response, whose downstream effects could alter OSN function and reduce olfactory sensitivities.