By now, most of us can probably list the recognised symptoms of coronavirus off the top of our heads: a new, continuous cough and a fever. But if you’ve suddenly lost your sense of smell, you might be wondering if that has something to do with Covid-19, too.
Anosmia, the complete loss of ability to smell, and hyposmia, a reduced ability to smell, are yet to be listed as symptoms of the virus by the NHS.
“Like many viruses that give infections of the upper respiratory tracts, there is a range of symptoms,” NHS England’s national medical director, Steve Powis, told HuffPost UK, in relation to questions about anosmia. “The two commonest are by far cough and a fever and that is exactly why they are the two symptoms that we are asking people to self-isolate if they get those symptoms.”
However, a growing number of people are reporting a loss of smell. Some also claim to have experienced loss of taste, but academics have pointed out taste perceptions often change as the result of what we can smell.
So is this linked to coronavirus? Here’s what we know so far.
Is it likely you’ve contracted Covid-19 if you’ve lost your sense of smell?
A number of conditions can cause anosmia and hyposmia – from the common cold to sinusitis and hay fever, states the NHS. So if you’re experiencing these symptoms, it doesn’t necessarily mean you’ve got Covid-19.
But Professor Carl Philpott, a smell expert based at UEA’s Norwich Medical School, says it does makes sense that a Covid-19 infection might cause this symptom.
“With viral shedding [the release of the virus] highest in the nose, it’s not surprising that the ‘unprotected’ smell receptor tissue at the top of the nose is vulnerable to infection,” he says.
Doctors are also reporting a rise in people presenting with total anosmia – also known as smell blindness. Professor Claire Hopkins of the British Rhinological Society says she’s seen four patients with the symptom just this week, where she usually sees no more than one a month.
And scientists at King’s College London have labelled loss of smell or taste a “key symptom for Covid-19 cases”. The scientists have been analysing data collected by The Covid Symptom Tracker app, where more than 1.8 million individuals have self-reported symptoms to aid research.
Data from the app shows 59% of people who’ve tested positive for Covid-19 in the UK reported loss of smell and taste, compared to only 18% of those who tested negative for the disease.
“These results were much stronger in predicting a positive Covid-19 diagnosis than self-reported fever,” the Kings College researchers said.
The UK research into anosmia and Covid-19 is still in its infancy, though. Professor Philpott points out some limitations to the Kings College research, highlighting the fact that many app users won’t have been tested for Covid-19. There’s also no data on the timing and severity of this symptom, he adds, and the research is only a snapshot over one week.
However, it does add to the “emerging evidence” from elsewhere around the world, says Prof. Philpott. In an open report addressed to Public Health England, ENT UK, the professional membership body representing ear, nose and throat clinicians, summarised the growing global evidence that anosmia might be a Covid-19 symptom.
“There is already good evidence from South Korea, China and Italy that significant numbers of patients with proven Covid-19 infection have developed anosmia/hyposmia,” they wrote. “In Germany it is reported that more than two in three confirmed cases have anosmia.”
Should you be worried if you can’t smell, then?
Suddenly losing your sense of smell can be disturbing, but it may ease your worries to know that anosmia has been recognised in individuals with mild cases of Covid-19, including those who’ve shown no other symptoms.
“In South Korea, where testing has been more widespread, 30% of patients testing positive have had anosmia as their major presenting symptom in otherwise mild cases,” the ENT UK report reads. “Iran has reported a sudden increase in cases of isolated anosmia, and many colleagues from the US, France and Northern Italy have the same experience.”
Social media is also full of testimonials from people saying they experienced temporary anosmia, but their sense of smell has since returned.
“So far with Covid-19, the smell loss appears to be transient but only as time elapses will we know how many people have a more permanent loss,” Prof. Philpott adds.
Losing your sense of smell doesn’t mean developing other symptoms is an inevitability, but of course, that can still happen. So while we wait for more research on the topic, make sure you’re clued up on other signs of infection and what to do if you feel you can’t manage your symptoms at home.
What should you do if you’ve lost your sense of smell?
The government advice remains that you only need to self-isolate if you have a high temperature or a new, continuous cough.
“We have nothing to add on this at this stage,” a Department of Health and Social Care spokesperson told HuffPost UK when asked about the emerging evidence around anosmia. “Our guidance on self-isolation has not changed and can be found on gov.uk.”
However, considering the fact that people with anosmia may have Covid-19 with no other symptoms, some experts are urging those affected to self-isolate anyway, as a precautionary measure, to limit the spread of the disease.
Professor Tim Spector, the lead researcher working on King’s College London’s app, said: “When combined with other symptoms, people with loss of smell and taste appear to be three times more likely to have contracted Covid-19 according to our data, and should therefore self-isolate for seven days to reduce the spread of the disease.”
Hazard perception is a big problem for those who experience anosmia, Professor Philpott previously told HuffPost UK. People may not being able to smell food that’s gone off, or may be unable to smell gas or smoke. So if you are experiencing this symptom, be extra vigilant with home safety and use-by dates.