A leading Australian ear, nose and throat surgeon has warned widely reported symptoms of loss of taste and smell in COVID-19 cases may linger long after some patients have recovered from the virus.

Key points: A growing body of scientific literature identifies anosmia and dysgeusia — the loss of smell and a diminished sense of taste — as coronavirus symptoms, alone or in conjunction with other symptoms

A growing body of scientific literature identifies anosmia and dysgeusia — the loss of smell and a diminished sense of taste — as coronavirus symptoms, alone or in conjunction with other symptoms A spokesperson for the Australian body representing ENT surgeons says those symptoms may last much longer than the virus for a minority of patients

A spokesperson for the Australian body representing ENT surgeons says those symptoms may last much longer than the virus for a minority of patients Testing criteria in Australia currently does not recognise anosmia and dysgeusia as COVID-19 symptoms without respiratory illness

Simon Carney, a spokesperson for the Australian Society of Otolaryngology, Head and Neck Surgery (ASOHNS), said he expected the incidence of patients experiencing ongoing loss of smell (anosmia) or diminished sense of taste (dysgeusia) could "go up quite significantly" following the outbreak.

But despite a growing body of scientific literature identifying anosmia and dysgeusia as signs of COVID-19, experiencing these symptoms alone will not yet qualify you for a test in Australia.

Calls to incorporate symptoms into testing guidelines

For nearly two weeks, rhinological and ENT bodies in both the UK and the US have been calling for anosmia to be added to the official lists of COVID-19 symptoms.

A peer-reviewed study approved for upcoming publication in the European Archives of Otorhinolaryngology has shown that in patients with only mild and moderate COVID-19 symptoms, 86 per cent experienced loss of smell and 88 per cent a loss of taste.

Results from a King's College London study in the process of being published found 59 per cent of patients reporting suspected COVID-19 symptoms to an app and who subsequently tested positive for COVID-19 reported losing their sense of smell and taste.

Those symptoms were a stronger predictor of coronavirus infection than fever.

A joint statement distributed to British doctors this week by the presidents of the British Rhinological Society concludes: "During the current COVID-19 pandemic, a patient presenting with new onset anosmia, in the absence of a head injury or nasal obstruction, should be considered likely to have COVID-19 infection."

Now the Australian body representing ear, nose, throat, head, and neck surgeons is calling for these symptoms to be incorporated into the Australian COVID-19 testing guidelines.

You may not know you have coronavirus

For many COVID-positive patients, anosmia has been an isolated symptom, without the other typical symptoms that we are associating with COVID-19, Professor Carney, from Flinders University, said.

That means people who have no other symptoms, or are perhaps only in the very early stages of the disease, could be going out in public and spreading the virus without realising they are infected.

"Loss of smell or loss of taste needs to be incorporated in the symptom guidelines in some way, whether it's a cardinal symptom or whether it's in association with other symptoms on a more mild basis," Professor Carney said.

"[Authorities] are trying to find these patients with the mild to moderate symptoms [because] they may be the ones that are allowing this community spread to continue.

"If we're really wanting to up to identify these patients with mild or moderate symptoms, then we need to start looking at what those symptoms are.

"Evidence [supporting the link] is emerging day by day."

However, it is important to note that losing your sense of smell or taste does not automatically mean you have COVID-19.

You can also temporarily lose your sense of smell if you have a very severe cold or very bad allergies.

No expansion of testing criteria yet

Symptoms affecting your olfactory (smell sensing) system are not recognised on the World Health Organisation's list of COVID-19 symptoms.

Australian authorities will not test a patient for COVID-19 without the presence of recognised symptoms, such as a cough, fever, sore throat or shortness of breath.

A spokesperson from the Department of Health said Australian authorities were currently not considering expanding the list of symptoms, but said the testing criteria was constantly under review depending upon the evolving epidemiology.

"Patients who present with atypical or uncommon symptoms, or who don't neatly fit the clinical and epidemiological criteria, will be assessed on a case-by-case basis to determine whether testing is warranted, and a degree of clinical discretion is inbuilt in the criteria," the spokesperson said.

"Just recently, Australia's testing criteria was broadened to ensure a wider net was put in place to capture people with higher pre-test chance of having the disease, but … without wasting testing on those [for] whom it is clearly not clinically warranted."

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Loss of smell and taste could last 'on a medium to long term'

Professor Carney said a minority of respiratory virus cases patients experienced ongoing problems with taste and smell, long after they had otherwise recovered.

While it is unclear what the prognosis will be for COVID-19-positive patients with those symptoms, Professor Carney said it was "highly likely" some people would experience permanent problems with their olfactory systems.

"I may see 25 patients a year who have got loss of smell from a common cold or another respiratory virus," he said.

"I unfortunately think that's going to go up quite significantly with patients with smell loss after COVID-19.

"We don't know enough about long-term loss of smell and COVID-19 patients, but certainly a lot of us are worried there will be long-term [implications] as a result of patients having these infections.

"I suspect we will see a large number of people who survived mild and moderate coronavirus infections may well have loss of a sense of smell on a medium to long term."

But don't panic yet

Even if you have a confirmed case of COVID-19 and have symptoms of anosmia or dysgeusia, Professor Carney said only some people may experience ongoing problems — and in any case, there are treatments available.

"There are new emerging treatments for loss of smell, such as vitamin drops you can put up the nose, which have produced some benefit in randomised controlled trials," he said.

"And there are ways to retrain the smell cells you you've been left with to become a wider spectrum."

He said there may be scales of damage, with patients who had completely lost both taste and smell likely to be worse affected than patients who had just lost their sense of smell.

"One of the big barometers we have about whether patients' smell loss is mild or more significant is whether they've still got their taste preserved," he said.

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"So if the patient reporting smell loss has still got their taste preserved, then it's often a milder loss of smell [so] that's usually a reassuring thing."

How does COVID-19 damage your smell?

Dr Carney said the damage to smell cells occurred in COVID-19 cases in the same way as other coronaviruses, including the common cold.

"The first thing a cold does is inflame the lining of your nose," he said.

"Swelling in the nose restricts the amount of airflow that can get up to the smell area, but also causes swelling in that sensory area, which means that the nerves that can detect the molecules are smothered by too much water in the tissues.

"There's also another way, but it tends to be later on.

"The virus tries to pretend it's a human cell, such as a smell cell, and therefore by the body producing antibodies to try and kill the coronavirus, it accidentally kills its own smell cells in the process."

Woman with no other symptoms apart from loss of taste and smell tests positive

Ms Lewis was diagnosed with COVID-19 despite her only symptoms being a loss of taste and smell. ( Supplied: Madeleine Lewis )

Performance artist Madeleine Lewis arrived into Brisbane from London on March 24 and experienced a sudden loss of taste and smell the following evening, but was experiencing no other symptoms and said she otherwise felt "fine".

"It's so weird, literally [the senses are] just completely absent," she said.

"I'm not craving eating anything because I can't even think of the concept of taste or smell.

"The only things I want to eat are really textured stuff.

"With the smell thing, you don't know how much you smell until all of a sudden it's gone.

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"It's just really completely disappeared, but I don't have a blocked nose at all."

She had heard from a family member that anosmia may be a symptom of COVID-19, so phoned the national coronavirus hotline to request a test.

However, the 32-year-old says she was told that loss of taste and smell were not considered symptoms of COVID-19 and therefore she was not eligible to be tested.

The following day she phoned 13-HEALTH reporting the same symptoms.

"I lied and said I had a sore throat [as well] because I knew I had it," Ms Lewis said.

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She was finally tested at the Royal Brisbane and Women's Hospital, where she received a positive result.

Ms Lewis said it was lucky she had heard "through the grapevine" about the link between anosmia and COVID-19 but many other patients may not be aware.

"I don't want to be told by the doctors 'you're all good', just because it's not considered a symptom," she said.

A week after being diagnosed, Ms Lewis said her sense of taste had partially returned, but her sense of smell remained absent.

"I can only really taste sweet and salty, but it's definitely improved a lot," she said.

"No smell though, so coffee still tastes like nothing."

She said she was hopeful her sense of smell would return soon.

"I know a girl in the UK [who lost her sense of smell] for two weeks, so I'm hoping I'm the same," she said.

What to do if you suddenly lose your sense of smell

Telehealth consultations are available for both GPs and specialist ENTs — so you should stay home, self-isolate and book in a telehealth consultation if you can.

If your doctor advises you to get a COVID-19 test and it is positive, Professor Carney said you should wait until you have recovered from coronavirus then make an appointment with an ENT specialist.

Your doctors can advise of early interventions available to help protect the degeneration of the smell centre, and then promote early recovery.

They are relatively low risk and could be followed for a month or two even without being formally examined by a doctor in person.

If you develop other symptoms of COVID-19, you should contact your GP or the Government's hotline (1800 020 080) to find out whether you are eligible for testing.