How does COVID-19 cause anosmia?

Anosmia is a frequent manifestation of COVID-19. However, questions remain regarding the time course and reversibility of COVID-19-related olfactory disorders, with some individuals experiencing persistent changes in olfaction after infection. Investigating the mechanisms behind olfactory dysfunction in COVID-19, Stanley Perlman, MD, PhD, University of Iowa, Iowa City, IA, details evidence from mouse models of COVID-19 that have shown a lack of viral infection of olfactory neurons. Instead, infection of the neighboring sustentacular cells has been shown, suggesting that SARS-CoV-2 infection affects smell not by directly infecting neurons but by affecting the function of vulnerable supporting cells. Current research suggests olfactory receptor downregulation and myeloid cell infiltration may play a role. Many questions remain regarding the mechanisms and implications of long term or permanent olfactory deficits resulting from COVID-19. One concern is that the inflammatory destruction thought to underlie anosmia may predispose individuals to an increased likelihood of neurological sequelae or neurodegenerative disorders in the long term. This interview took place during the 2021 International Congress of Parkinson's Disease and Movement Disorders.