Olfactory training in long COVID-19 patients with lasting symptoms including olfactory dysfunction.

Introduction: Two-thirds of patients with COVID-19 developed smell and taste dysfunction, of whom half experienced improvement within the first month. After six months, 5-15% still suffered from significant olfactory dysfunction (OD). Before COVID-19, olfactory training (OT) was proved to be effective in patients with post-infectious OD.

[The nose can be the focus of treatment and prophylactic approaches against COVID-19].

Infection with SARS-CoV-2 frequently commences in the nasal cavity, yet knowledge about this initial virus-host interaction is sparse. In this review, we update our current understanding of SARS-CoV-2 infection via the nasal epithelium and the associated local immune response. Furthermore, we present considerations to how this interaction may influence the clinical course of COVID-19 and the systemic immune response, and lastly touch upon the potential for intranasal vaccination, intranasal antiviral therapies and immunomodulatory approaches.