How COVID-19 causes smell loss

Snell loss or loss of taste has emerged as a common symptom in patients with mild cases of COVID-19. Now a new study shows that while those senses return within a month for most people, some can struggle with the unsettling changes for longer.

The loss of smell, in particular, has been seen in people who ultimately test positive for the new coronavirus while having no other symptoms, according to the American Academy of Otolaryngology — Head and Neck Surgery.

That’s led to questions about whether “smell tests” — in addition to temperature checks — could be an effective way to screen people for COVID-19 in airports, theme parks and other public places.

Temporary smell loss, or anosmia, is the main neurological symptom and one of the earliest and most commonly reported indicators of COVID-19. Studies suggest it better predicts the disease than other well-known symptoms such as fever and cough, but the underlying mechanisms for smell loss in patients with COVID-19 have been unclear.

A majority of COVID-19 patients experience some level of smell loss, most often temporary, according to emerging data. Analyses of electronic health records indicate that COVID-19 patients are 27 times more likely to have smell loss but are only around 2.2 to 2.6 times more likely to have fever, cough or respiratory difficulty, compared to patients without COVID-19. What does this mean for predicting who suffers from COVID-19?

COVID-19 patients typically recover their sense of smell over the course of weeks — much faster than the months it can take to recover from anosmia caused by a subset of viral infections known to directly damage olfactory sensory neurons (the nerves in the nose that transmit smells). In addition, many viruses cause temporary loss of smell by triggering upper respiratory issues such as stuffy nose. Some COVID-19 patients, however, experience a loss of smell without any nasal obstruction.

So if you feel that you have had a change in smell or taste from your normal self, you should self-quarantine and get tested for the coronavirus.

Materials provided by Harvard Medical School.