COVID-19 Symptoms: SARS-CoV-2 Not Only Causes Anosmia But Also Parosmia Or Smell Distortion And Experiences Of 'Disgusting' Smells Of Fish And Sulphur

COVID-19 Symptoms: According to researchers and medical professionals, a majority of recovering COVID-19 patients and also those undergoing Long COVID conditions will also end up suffering from parosmia with frequent experiences of foul and disgusting smells. This condition can last for weeks or even months.

Although anosmia  or loss of smell is a coronavirus symptom, but some with long COVID are detecting unpleasant odours months after catching the virus.
 
Individuals suffering from long COVID are reporting a strong smell of fish, sulphur and a sweet sickly odour, as further symptoms of the SARS-CoV-2 coronavirus emerge.
 
Parosmia is the medical term for experiencing distortions of the sense of smell. Someone with parosmia may be able to detect odours, but the smell of certain things or sometimes everything – is different, and often unpleasant.
 
Parosmia can usually be traced back to an infection or brain trauma. When parosmia is triggered by medication, chemical exposure, or smoking, it usually subsides once the trigger is removed. Less often, parosmia is caused by a sinus polyp, a brain tumor, or is an early sign of certain neurological conditions.
 
Parosmia is sometimes confused with another condition called phantosmia, which causes you to detect a “phantom” scent when there’s no scent present.
 
Parosmia is different because people who have it can detect an odor that’s present, but the scent smells “wrong” to them. For example, the pleasant odor of freshly baked bread might smell overpowering and rotten instead of subtle and sweet.
 
People experience a wide range of parosmia for an array of different reasons. In the most severe cases, parosmia can cause you to feel physically ill when your brain detects strong, unpleasant scents.
 
This unusual side-effect may be disproportionately affecting young people and healthcare workers.
ENT (Ear, nose and throat) surgeon Professor Dr Nirmal Kumar called the symptom "very strange and very unique".
 
Dr Kumar who is also the president of ENT UK, was among the first medics to identify anosmia  ie loss of smell as a coronavirus indicator in March.
 
Dr Kumar urged the Public Health England to add it to the symptom list months before it became official guidance.
 
He told Thailand Medical News,”It is really disturbing patients and their quality of life is hugely impacted".
 
The term Long COVID is used to describe the effects of coronavirus that can continue for weeks or months beyond the initial illness.
 
Of more than 4,000 respondents to a multilingual, international study of people with recent smell loss published in Chemical Senses in June, 7 percent reported parosmia, or odor distortion. Facebook support groups dedicated to parosmia and phantosmia, the clinical names for specific smell disorders, have grown drastically in the past few months. Instead of a scentless world, an increasing number of people who lost their sense of smell because of Covid- 19 are complaining that things just don’t smell right. https://academic.oup.com/chemse/article/45/7/609/5860460
 
They no longer wake up and can’t smell the coffee; because of parosmia, their coffee smells like burning rubber or sewage. Parosmia is most often an unpleasant smell, a distortion of an actual odor, making many foods smell and taste revolting. Phantosmia is more random, occurring without a scent trigger, uninvited and unwanted. Phantosmias, which can be fleeting or linger, are also usually foul smells, often cigarette smoke or burning wood.
 
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Dr Zara M. Patel, the director of endoscopic skull base surgery at the Stanford School of Medicine, has been studying olfactory dysfunction for more than a decade. It’s not unusual, she says, for smell distortions to accompany or follow smell loss.
 
Dr Patel said, “There are so many viruses that can cause smell loss, not only other coronaviruses, but also influenza viruses and rhinoviruses. Many of these viruses also will lead to a parosmia and phantosmia, either as part of the initial deficit, or as the nerves try and recover, but make aberrant connections.”

Anosmia or smell loss is such a prevalent symptom of COVID-19 it can be used for diagnosis. A May study in the Annals of Internal Medicine found 86 percent of the COVID-positive patients experienced smell loss. https://www.acpjournals.org/doi/10.7326/M20-2428
 
Most individuals who suffer from sudden onset anosmia from the SARS-CoV-2 infection recover their smell quickly, within four weeks for 89 percent of those in a recent study in JAMA Otolaryngology. But the remaining 10 percent continued to experience smell loss or distortions. https://jamanetwork.com/journals/jamaotolaryngology/article-abstract/2767781
 
In the journal: Science Advances, researchers from Harvard Medical School reported that through bulk sequencing of mouse, non-human primate and human olfactory cells, they located a source of these proteins on the sustentacular cells, which support the olfactory receptor neurons and help transport odor information through the nasal mucus. https://advances.sciencemag.org/content/6/31/eabc5801
 
Dr Patel told Thailand Medical news, “SARS-CoV-2 binds to ACE receptors, which are present in the basal cells, supporting cells and perivascular cells around the neurons in the olfactory epithelium. So although the neuron itself is not damaged, all the support structure around it is.”
 
She added, “Those cells that support the regenerative capacity are the ones that suffer. We also know that nerves do not function very well within an inflammatory environment. So because of all those reasons, it is not surprising this virus causes smell dysfunction.”
 
Dr Kumar meanwhile said that he has noted that among the thousands of patients being treated for long-term anosmia across the UK, some are experiencing parosmia.
 
Dr Kumar told Thailand Medical News that patients experience olfactory hallucinations, meaning "sense of smell is distorted, and mostly unpleasantly, unfortunately".
 
Dr Kumar explained, “The SARS-CoV-2 virus is a ‘neurotropic virus.’ This virus has an affinity for the nerves in the head and in particular, the nerve that controls the sense of smell. But it probably affects other nerves too and it affects, we think, neurotransmitters ie the mechanisms that send messages to the brain."
 
Dr Kumar added, "Some individuals are reporting hallucinations, sleep disturbances, alterations in hearing. We don't know exact mechanisms, but we and finding ways to try and help patients recover."
 
A 24-year-old banker living in London, Daniel Saveski said he lost his sense of taste and smell for two weeks after contracting coronavirus in March, and has been suffering with parosmia since.
 
From West Yorkshire, Saveski, said strong-smelling things like bins now have a burning, sulphur-like odour, or smell "like toast. It's lessened my enjoyment of food, and it's a bit depressing not being able to smell certain foods."
 
The organization: Charity AbScent, which supports individuals with smell disorders, is gathering information from thousands of anosmia and parosmia patients in partnership with ENT UK and the British Rhinological Society to aid the development of therapies.
 
Charity AbScent recommends anyone affected by parosmia to undergo "smell training", which involves sniffing rose, lemon, clove and eucalyptus oils every day for around 20 seconds in a bid to slowly regain their sense of smell.
 
Dr Kumar said: "There are some promising early reports that such training helps patients." He added that most people will eventually get their normal sense of smell back.
 
As of now, doctors have little relief to offer. In the past, clinicians have deployed antipsychotic, antimigraine, and antiseizure medications, corticosteroids, transcranial stimulation and even topical cocaine for relief from phantosmia and parosmia. An international group of olfactory experts writing in Rhinology advised that no definitive evidence can be found for the efficacy of any specific medical treatment for smell disorders. https://pubmed.ncbi.nlm.nih.gov/28623665/
 
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