From the first reports coming out of Wuhan, Iran and later Italy, we knew that losing your sense of smell (anosmia) was a significant symptom of the disease. Now, after months of reports, both anecdotal and more rigorous clinical findings, we think we have a model for how this virus may cause smell loss.
One of the most common causes of smell loss is a viral infection, such as the common cold, sinus or other upper respiratory tract infections. Those coronaviruses that don't cause deadly diseases, such as COVID-19, SARS and MERS, are one of the causes of the common cold and have been known to cause smell loss.
In most of these cases, sense of smell returns when symptoms clear, as smell loss is simply the result of a blocked nose, which prevents aroma molecules reaching olfactory receptors in the nose. In some cases, smell loss can persist for months and years.
For the novel coronavirus (SARS-CoV-2), however, the pattern of smell loss is different. Many people with COVID-19 reported a sudden loss of sense of smell and then a sudden and full return to a normal sense of smell in a week or two.
Interestingly, many of these people said their nose was clear, so smell loss cannot be attributed to a blocked nose. For others, smell loss was prolonged and several weeks later they still had no sense of smell. Any theory of anosmia in COVID-19 has to account for both of these patterns.
This sudden return of a normal sense of smell suggests an obstructive smell loss in which the aroma molecules cannot reach the receptors in the nose (the same type of loss one gets with a clothes peg on the nose).
Now that we have CT scans of the noses and sinuses of people with COVID-19 smell loss, we can see that the part of the nose that does the smelling, the olfactory cleft, is blocked with swollen soft tissue and mucus known as a cleft syndrome. The rest of the nose and sinuses look normal and patients have no problem breathing through their nose.
Location of the olfactory bulb. (medicalstocks/iStock/Getty Images Plus)
We know that the way SARS-CoV-2 infects the body is by attaching to ACE2 receptors on the surface of cells that line the upper respiratory tract. A protein called TMPRSS2 then helps the virus invade the cell.
Once inside the cell, the virus can replicate, triggering the immune system's inflammatory response. This is the starting point for the havoc and destruction that this virus causes once in the body.
Initially, we thought that the virus might be infecting and destroying the olfactory neurons. These are the cells that transmit the signal from the aroma molecule in your nose to the area in the brain where these signals get interpreted as "smell".
Olfactory neuron [pink] with protruding smell receptors. (Steve Gschmeissner/Getty Images)
However, an international collaboration showed recently that the ACE2 proteins the virus needs to invade the cells were not found on the olfactory neurons. But they were found on cells called "sustentacular cells", which support the olfactory neurons.
We expect that these support cells are likely to be the ones that are damaged by the virus, and the immune response would cause swelling of the area but leave the olfactory neurons intact. When the immune system has dealt with the virus, the swelling subsides and the aroma molecules have a clear route to their undamaged receptors and the sense of smell returns to normal.
So why does smell not return in some cases? This is more theoretical but follows from what we know about inflammation in other systems. Inflammation is the body's response to damage and results in the release of chemicals that destroy the tissues involved.
When this inflammation is severe, other nearby cells start to be damaged or destroyed by this "splash damage". We believe that accounts for the second stage, where the olfactory neurons are damaged.
Recovery of smell is much slower because the olfactory neurons need time to regenerate from the supply of stem cells within the lining of the nose.
Initial recovery is often associated with distortion of the sense of smell known as parosmia, where things don't smell like they used to. For many parosmics, for instance, the smell of coffee is often described as burnt, chemical, dirty and reminiscent of sewage.
Olfaction has been called the Cinderella of the senses because of its neglect by scientific research. But it has come to the forefront in this pandemic. The silver lining is that we will learn a lot about how viruses are involved in smell loss from this. But what hope is there for people with a loss of smell now?
The good news is that the olfactory neurons can regenerate. They're regrowing in almost all of us, all of the time. We can harness that regeneration and guide it with "physiotherapy for the nose": smell training.
There is solid evidence that many forms of smell loss are helped by this repeated, mindful exposure to a fixed set of odorants every day and no reason to think it won't work in COVID-19 smell loss.
Simon Gane, Consultant Rhinologist and ENT surgeon, City, University of London and Jane Parker, Associate Professor, Flavour Chemistry, University of Reading.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
See the original post:
COVID-19 Can Cause Loss of Smell, And Scientists Finally Discovered Why - ScienceAlert
- Technion team discovers important adaptive strategy of the microbiome, impacting immune system - The Jerusalem Post - April 16th, 2024
- Targeting aging and age-related diseases with vaccines - Nature.com - April 16th, 2024
- Single cell analysis unveils B cell-dominated immune subtypes in HNSCC for enhanced prognostic and therapeutic ... - Nature.com - April 16th, 2024
- After the Smoke Clears: Scars on the Immune System - The Scientist - April 16th, 2024
- Exercise and the Immune System: What's the Latest Research? - Technology Networks - April 16th, 2024
- Analysis of immune cell infiltration characteristics in severe acute pancreatitis through integrated bioinformatics ... - Nature.com - April 16th, 2024
- Vaccination impairs de novo immune response to omicron breakthrough infection, a precondition for the original ... - Nature.com - April 16th, 2024
- Harnessing the power of the body's own cells to defeat cancer - Press Publications Inc. - April 16th, 2024
- Best Life: Immunotherapy targets brain cancer - Action News 5 - April 16th, 2024
- Dietary factors and their influence on immunotherapy strategies in oncology: a comprehensive review | Cell Death ... - Nature.com - April 16th, 2024
- New insights on B cells: Researchers explore building better antibodies and curbing autoimmune diseases - Medical Xpress - April 16th, 2024
- Immune cells' intense reaction to the coronavirus may lead to pneumonia - Science News Magazine - April 16th, 2024
- The telltale traces long Covid leaves in the blood - healthcare-in-europe.com - April 16th, 2024
- Overview of the Immune System - The Merck Manuals - March 18th, 2024
- SUNDAY Unraveling The Gut-Brain Connection: How Infant Gut Bacteria Shape Immune Resilience | TheHealthSit - TheHealthSite - March 18th, 2024
- Making drugs from T cells: The quantitative pharmacology of engineered T cell therapeutics | npj Systems Biology and ... - Nature.com - March 18th, 2024
- Study unlocks the mystery of neonatal neutropenia in newborns - News-Medical.Net - March 18th, 2024
- Vertebral Subluxation and Systems Biology: An Integrative Review Exploring the Salutogenic Influence of Chiropractic ... - Cureus - March 18th, 2024
- A new strategy to attack aggressive brain cancer shrank tumors in two early tests - ABC News - March 18th, 2024
- Turning on the Bat Signal - The Scientist - March 18th, 2024
- Power Foods That Can Support Your Immune System - Videos from The Weather Channel - The Weather Channel - March 18th, 2024
- Report: Aggressive brain tumors respond to new, immune-focused therapy - UPI News - March 18th, 2024
- Designer immune-cell therapy could shrink deadly brain tumors, early trials show - Livescience.com - March 18th, 2024
- 20.2: Introduction to the Immune System - Biology LibreTexts - February 27th, 2024
- Can one shot of yoghurt really boost your immunity and gut health? - Daily Mail - February 27th, 2024
- New cancer therapy approved by FDA supercharges bodys immune system - The Washington Post - February 27th, 2024
- How bubonic plague rewired the human immune system - BBC.com - February 27th, 2024
- Innovative therapy targets and destroys leukemia stem cells - News-Medical.Net - February 27th, 2024
- Participate in Our Study for $100; Open Slots This Week - University of Arkansas Newswire - February 27th, 2024
- Sexual dimorphism during integrative endocrine and immune responses to ionizing radiation in mice | Scientific Reports - Nature.com - February 27th, 2024
- Comprehensive pan-cancer analysis identifies the RNA-binding protein LRPPRC as a novel prognostic and immune ... - ScienceDirect.com - February 27th, 2024
- YOUR HEALTH: The HAMR fights cancer - WAFB - February 27th, 2024
- Cycles of a diet that mimics fasting can reduce signs of immune system aging, as well as insulin resistance and liver fat - News-Medical.Net - February 27th, 2024
- How the powerhouse of the cell could be cancers Achilles heel - Freethink - February 27th, 2024
- Food is medicine: The science behind zinc and other supplements for immune health - Healio - February 27th, 2024
- Unleashing Our Immune Response to Quash Cancer - Medscape - February 27th, 2024
- Tumor histoculture captures the dynamic interactions between tumor and immune components in response to anti-PD1 ... - Nature.com - February 27th, 2024
- Converging and evolving immuno-genomic routes toward immune escape in breast cancer - Nature.com - February 27th, 2024
- Sanjula Jain Urges a Comprehensive Approach in Address Alarming Rise in Cancer Cases Among Younger Populations - Managed Healthcare Executive - February 27th, 2024
- Cystic fibrosis breakthrough points to zinc as infection buster - New Atlas - February 27th, 2024
- Exploring synergies between B- and T-cell vaccine approaches to optimize immune responses against HIVworkshop ... - Nature.com - February 27th, 2024
- Is the 100-year old TB vaccine a new weapon against Alzheimers? - The Guardian - February 27th, 2024
- Immune system in the blood of Alzheimer's patients found to be epigenetically altered - News-Medical.Net - February 10th, 2024
- What impact does exercise have on your immune system? And how to stay well while cycling - BikeRadar - February 10th, 2024
- Had COVID recently? Here's what to know about how long immunity lasts, long COVID, and more - AAMC - February 10th, 2024
- Noor Momin harnesses the immune system to treat heart disease | Penn Today - Penn Today - February 10th, 2024
- Research reveals a process tumors use to induce immune suppressor cells and evade immunotherapy - Medical Xpress - February 10th, 2024
- Immune targeting of HIV-1 reservoir cells: a path to elimination strategies and cure - Nature.com - February 10th, 2024
- Preventing severe allergic reactions with nanoparticles - National Institutes of Health (NIH) (.gov) - February 10th, 2024
- Sugary handshakes are how cells talk to each other understanding these name tags can clarify how the immune ... - The Conversation Indonesia - February 10th, 2024
- Scientists have identified an immune cell that can cause allergies - EL PAS USA - February 10th, 2024
- Sickle cell and the importance of the immune system - Punch Newspapers - February 10th, 2024
- Which cancers can be treated with immune checkpoint inhibitors? - MD Anderson Cancer Center - February 10th, 2024
- How does waste leave the brain? Washington University School of Medicine in St. Louis - Washington University School of Medicine in St. Louis - February 10th, 2024
- Healthy Kids: Give your immune system a boost to stay healthy this winter - nbc16.com - February 10th, 2024
- The impact of prior exposure to hypoglycaemia on the inflammatory response to a subsequent hypoglycaemic episode ... - Cardiovascular Diabetology - February 10th, 2024
- Impact of Chronic Stress on Immune System and Depression | Health News - Medriva - February 10th, 2024
- I tried 'swamp soup,' the viral recipe that promises to boost your immune system - Yahoo News - February 10th, 2024
- Understanding Immune Checkpoint Inhibition Therapy: Challenges and Strategies - Medriva - February 10th, 2024
- One Simple Change May Dramatically Boost The Effect of COVID-19 Vaccines - ScienceAlert - February 10th, 2024
- The gut virome is associated with stress-induced changes in behaviour and immune responses in mice - Nature.com - February 10th, 2024
- Cancer vaccines are in the works to fight BRCA-linked gene mutations - The Philadelphia Inquirer - February 10th, 2024
- What are the organs of the immune system? - InformedHealth.org - NCBI ... - January 17th, 2024
- Novel insights into the immune response to bacterial T cell superantigens - Nature.com - January 17th, 2024
- FDA signs off on Takeda's HyQvia as maintenance therapy for CIDP - FiercePharma - January 17th, 2024
- CBDs Pobezinsky and Pobezinskaya Use Flow Cytometry to Determine How Tumor Cells Outwit the Bodys Immune ... - UMass News and Media Relations - January 17th, 2024
- Boosting. What To Do. - Science Based Medicine - January 17th, 2024
- Axelia Oncology takes its TLR2/6 agonist into the clinic to harness the innate immune system - BioWorld Online - January 17th, 2024
- Long COVID manifests with T cell dysregulation, inflammation and an uncoordinated adaptive immune response to ... - Nature.com - January 17th, 2024
- Opinion | Thanks to mRNA, Future Drugs Will Be Easier and Faster to Make - Mississippi Free Press - January 17th, 2024
- Elon research team models the COVID immune response, one equation at a time - Today at Elon - January 17th, 2024
- Are plant-based meals good for your immune system? 4 things to know about improving your health this week. - Yahoo Life - January 17th, 2024
- Scientists Find Key To Potential Breast Cancer Prevention, Treatment | Newsroom - UNC Health and UNC School of Medicine - January 17th, 2024
- What if every germ hit you at the exact same time? An immunologist explains - The Conversation - January 17th, 2024
- Why Don't We Have a Staph Vaccine? - Healthnews.com - January 17th, 2024
- Best ways to improve your immune system - The Business Standard - January 17th, 2024
- Stanford University researchers think future pandemics could be prevented with universal vaccines - KGO-TV - January 17th, 2024
- Why you may feel depressed and anxious when you're ill and how to cope with it - The Conversation - January 17th, 2024
- New mechanism with potential to boost checkpoint-blocking cancer immunotherapies identified - Medical Xpress - January 17th, 2024
- Battling Bugs and Blues: The Interplay of Infection and Emotion - News-Medical.Net - January 17th, 2024