When a person partially or completely loses their sense of smell.
Temporary loss of smell (anosmia) and taste appears to mainly present as early signs of COVID-19 and are the main neurological and most commonly reported symptoms of the disease. Most patients report a sudden loss of smell followed by either a full recovery in a week or two or a permanent loss of smell (see Long COVID). A study in PLOS Medicine reported that four out of five people who reported anosmia, tested positive for SARS-CoV-2, with 40% of them not reporting dry cough or fever which are common symptoms.
Viruses often affect, and remove, the small hair-like endings of receptor cells in our noses. Scientists, however, suggest the novel coronavirus may cause an inflammation of the nerves which transmit the signal from the nose to the brain. There is already substantial evidence to suggest that the virus affects both our nervous and breathing systems.