Although cough and fever are the two most common symptoms of COVID-19, the inability to smell or taste is possibly the most interesting and unique. Viral infections are one of the most common causes of lost ability to smell, called “anosmia”. There are hundreds of viruses that can cause this symptom, including other viruses in the coronavirus family of viruses. As such, it may be no surprise that COVID-19 does as well.
Doctors are not certain of the cause of these symptoms, but they may result from damage to the smell receptor cells in the nose as well as nasal congestion. What about taste? Well, it seems that when people report loss of taste, this may really be a function of losing the sense of smell, as smell is such an important part of taste.
Overall, the reports about loss of sense of smell are largely anecdotal, and it is unclear if this symptom is a strong enough predictor of COVID-19 to be used to diagnose it. However, this has not stopped organizations like the American Academy of Otorhinolaryngology – Head and Neck Surgery from suggesting that these symptoms should be “added to the list of screening tools for possible COVID-19 infection”, and even that having these symptoms without other diseases of the nose may “warrant serious consideration for self-isolation and testing of these individuals.”