What’s behind this sudden loss of smell?
Helen Chandlerwilde talks to the experts about the new symptoms that could be warning signs of Covid-19
By now you are probably well aware that a cough, shortness of breath or high temperature are all warning signs of Covid-19, and anyone who experiences them needs to self-isolate for seven days. But another odd symptom seems to be a calling card: a sudden loss of smell.
The symptom appears to be incredibly common even though it is not yet widely acknowledged in the UK. More than two thirds of those with coronavirus in Germany report losing their sense of smell, and 30 per cent of sufferers in South Korea had anosmia as their main symptom, according to a report from ENT UK, an organisation that represents ear, nose and throat surgeons.
The smell loss associated with coronavirus is different to that which you might get with a normal cold, says Prof Claire Hopkins, president of the British Rhinological Society. “Typically when you have a cold your nose is congested, and therefore no one is surprised you can’t smell,” she says. “But what’s happening here is there is no nasal obstruction, so people are surprised.”
The best guess of experts so far seems to be that Covid-19 is affecting the smell nerves in the nose.
“We have seen evidence showing how the virus has the ability to affect the nerves, and the smell nerves are the only bits that are exposed in a way that no other nerves are,” says Carl Philpott, professor of rhinology at the University of East Anglia. He believes that the virus causes neuronitis, or inflammation of the nerves in the nose, which stops them from performing as they should.
Doing further research at present is difficult, says Prof Philpott: “We would need to examine the noses, and that’s what we’re telling people not to do as it puts the doctor at massive risk.”
Worryingly, anosmia can appear entirely by itself and without the “typical” coronavirus symptoms, which means that many will not be aware that they have it. This seems to be fairly common: in a study of suspected coronavirus sufferers with smell loss, one in six had it as the only symptom, according to Prof Hopkins.
A further one in 10 lost their sense of smell before getting other symptoms, which shows that they could be spreading infection before reaching the criteria that require self-isolation. Prof Hopkins has seen this in her own life: “A colleague told me he lost his sense of smell 48 hours before. He got a private test which was positive, which meant he could stay away and not infect patients.”
Anosmia appearing without other symptoms is something we should be aware of, says Prof Nirmal Kumar, president of ENT UK. “The spreading of it is difficult because these patients aren’t terribly unwell, so they are walking around as if nothing is wrong,” he says.
This seems to be particularly the case with younger people: “I saw nine young people with loss of sense of smell who were otherwise fit and well this month. That’s extremely unusual, I might usually see one a month,” says Prof Hopkins.
Some patients who are reporting smell loss are also saying that they have lost their ability to taste. The likelihood is they are mistaking smell for taste, says Prof Philpott. “When you’re eating, 80 per cent of what you appreciate of flavour is the smell, so people think they can’t taste even though they can still get salty, sweet, bitter and sour.”
Some patients are even experiencing dysgeusia: things tasting different to normal. Most people suffering this are describing a “metallic taste”, says Prof Hopkins.
The good news is that the coronavirus-induced anosmia looks like it will be temporary; most patients who have reported it so far describe their sense of smell returning within a fortnight.
It could be that smell loss is not the only symptom of coronavirus that the UK is not yet picking up on. France’s diagnostic test asks 23 questions that cover sore throat, tiredness and aches, as well as loss of smell and taste.
The most important thing is to take smell loss seriously. If you have suddenly lost your sense of smell, you should follow the recommendations for those with a new cough or temperature, says Prof Kumar, and isolate yourself for at least seven days.
‘I saw nine young people with loss of sense of smell this month’