Loss of smell in Covid-19. Illustration of a section through the brain of a woman being infected with SARS-Cov-2 virus particles (blue), the cause of Covid-19. The olfactory bulb (green), located in the forebrain, has many olfactory receptor cells that project into the lining of the nasal cavity and detect smell molecules. The olfactory bulb relays information from the receptors to other parts of the brain, including the olfactory cortex (deep blue), which is responsible for the conscious perception of smell, the hippocampus (purple), which is responsible for olfactory memory, and the amygdala (pink), which is responsible for the emotional response to smell. Loss of smell (anosmia) is a common symptom of Covid-19, especially in those that are otherwise asymptomatic. The exact mechanism by which the virus causes anosmia is not known.