The loss of smell that can accompany coronavirus is unique and different from that experienced by someone with a bad cold or flu, say European researchers who have studied the experiences of patients.
When Covid-19 patients have smell loss it tends to be sudden and severe.And they usually don't have a blocked, stuffy or runny nose - most people with coronavirus can still breathe freely.
Another thing that sets them apart is their "true" loss of taste.
It's not that their taste is somewhat impaired because their sense of smell is out of action, say the researchers in the journal Rhinology. Coronavirus patients with loss of taste really cannot tell the difference between bitter or sweet.
Experts suspect this is because the pandemic virus affects the nerve cells directly involved with smell and taste sensation.
The main symptoms of coronavirus are:
-high temperature-new, continuous cough
-loss of smell or taste
Anyone with these symptoms should self-isolate and arrange to have a swab test to check if they have the virus. Members of their household should isolate too to prevent possible spread.
Lead investigator Prof Carl Philpott, from the University of East Anglia, carried out smell and taste tests on 30 volunteers: 10 with Covid-19, 10 with bad colds and 10 healthy people with no cold or flu symptoms.
Smell loss was much more profound in the Covid-19 patents. They were less able to identify smells, and they were not able to discern bitter or sweet tastes at all.
He stressed that diagnostic throat and nose swab tests were still essential if someone thought they might have coronavirus.
The senses of smell and taste return within a few weeks in most people who recover from coronavirus, he added.