[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/7260\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EWhy does coronavirus make people lose their sense of smell?\u003C\/h2\u003E\u003Cp\u003EThe link with coronavirus was brought to public attention by \u003Ca href=\u0022https:\/\/www.entuk.org\/research-and-innovation\/sites\/default\/files\/hm\/files\/Loss%20of%20sense%20of%20smell%20as%20marker%20of%20COVID.pdf\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Especialists in the UK\u003C\/a\u003E in \u003Ca href=\u0022https:\/\/www.bmj.com\/content\/368\/bmj.m1202\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Elate March\u003C\/a\u003E, and since then health organisations have gradually added anosmia to the list of symptoms for Covid-19. According to a recent study, about two-thirds of people with Covid-19 experience a sudden loss in \u003Ca href=\u0022https:\/\/www.nature.com\/articles\/s41591-020-0916-2\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Esmell or taste\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EProfessor Noam Sobel from the Weizmann Institute of Science in Israel and his lab are experts in our sense of smell, or olfaction.\u003C\/p\u003E\u003Cp\u003E\u2018An ex-member of our lab, who had since moved to London, caught Covid-19 and became completely anosmic. So we had really detailed reports from our friend who, unlike most people, was very, very well trained in describing his olfactory experience,\u2019 he said.\u003C\/p\u003E\u003Cp\u003EThis gave the lab a reliable, if anecdotal, description of the role of anosmia. In this particular case, the total loss of smell happened a day after the appearance of other symptoms. That made Prof. Sobel wonder if a more subtle, gradual loss of smell could be a much-needed early warning of Covid-19. However, the challenge is to find a way to detect that.\u003C\/p\u003E\u003Cp\u003E\u0027Humans are notoriously poor at reporting on their own sense of smell. If I were to ask you if your sense of smell today is slightly better or worse than it was yesterday, you would not notice mild changes,\u0027 he said.\u003C\/p\u003E\u003Cp\u003EThis led Prof. Sobel to create the \u003Ca href=\u0022https:\/\/smelltracker.org\/\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003ESmell Tracker\u003C\/a\u003E, an online system that uses common household items, such as honey, garlic and toothpaste, for the public to test their sense of smell.\u003C\/p\u003E\u003Cp\u003EAlready 14,000 people have used it to help identify changes in their sense of smell. Prof. Sobel hopes that if it becomes more widely used then it could also help policymakers to track the spread of the disease in different regions. Already, the tracker\u2019s popularity in Sweden allowed the researchers to identify a peak in anosmia around 15 April.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EOlfactory bulb\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThe cause of coronavirus-related anosmia is still unknown, but our understanding of how smell works is helping narrow it down.\u003C\/p\u003E\u003Cp\u003E\u2018It\u2019s not that the nose is blocked with mucus \u2013 that would be the simplest explanation,\u2019 said Dr Matthew Grubb, from King\u2019s College London in the UK. He is a neuroscientist specialising in the olfactory bulb, the first region of the brain responsible for processing our sense of smell.\u003C\/p\u003E\u003Cp\u003EAlmost all of our brain cells are created by the time we are born, and they can last a lifetime. The mammalian olfactory bulb is almost unique in continually producing new neurons throughout adult life. It is this behaviour that drew Dr Grubb into this area of research.\u003C\/p\u003E\u003Cp\u003E\u2018I still find it fascinating. Building a brain from scratch is hard enough, with its intricate connectivity between the cells\u2026 But then introducing new cells into it, you can imagine that would have the potential to really mess things up,\u2019 he said.\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018It\u2019s not that the nose is blocked with mucus \u2013 that would be the simplest explanation.\u2019\u0026amp;nbsp;\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EDr Matthew Grubb, King\u2019s College London, UK\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003EIt is still not clear why the olfactory bulb does this. One idea is that having lots of young neurons allows the bulb to adapt more easily to changes. Dr Grubb is running a project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/rcn\/209498\/en\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EFuncoplan\u003C\/a\u003E to understand whether new cells respond differently to changes in the environment.\u003C\/p\u003E\u003Cp\u003EIn March, he co-wrote a \u003Ca href=\u0022https:\/\/www.biorxiv.org\/content\/10.1101\/2020.03.25.009084v4\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Eresearch paper\u003C\/a\u003E setting out potential causes of anosmia in Covid-19 patients.\u003C\/p\u003E\u003Cp\u003E\u2018(Olfactory) sensory neurons (in the nose) are the cells that do the detecting of odour and stimuli and send those signals to the brain. If they die, then you don\u2019t lose them forever. They can regenerate, but that takes a few weeks,\u2019 he said.\u003C\/p\u003E\u003Cp\u003E\u2018The fact that the recovery (of the sense of smell) seems to be a bit quicker with Covid-19 started to make people think that maybe it\u2019s not infecting the neurons themselves.\u2019\u003C\/p\u003E\u003Cp\u003EThis shifted attention away from neurons to different types of cells that can regenerate quickly. In particular, ones known as sustentacular cells, which provide support for the olfactory sensory neurons.\u003C\/p\u003E\u003Cp\u003EThese supporting cells can produce high levels of ACE2, a protein that the coronavirus uses to invade the cell. By comparison, the olfactory neurons have no ACE2, meaning that they pass unnoticed by the virus.\u003C\/p\u003E\u003Cp\u003EOne idea is that those supporting cells are getting infected and dying off, says Dr Grubb. \u2018Without the support cells, the neurons can\u2019t function anymore. Once those supporting cells regenerate themselves, which can happen quite quickly, then the neurons can function once more and people can smell again.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ELoss\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EProf. Sobel has been receiving \u2018countless\u2019 emails from people worried about their loss of smell. Mostly, the worry comes from the possibility that it will not come back, which it has done so far for the vast majority.\u003C\/p\u003E\u003Cp\u003EHe says that our sense of smell fits with the clich\u00e9 of \u2018not noticing how important it is until you lose it.\u2019 A big part of his work is to show just how important the sense of smell is in social interactions.\u003C\/p\u003E\u003Cp\u003E\u0027We have this view that social chemo-signalling is a big part of human social behaviour,\u0027 he said. Through a project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/670798\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003ESocioSmell\u003C\/a\u003E, he is investigating this idea across different aspects of social interactions.\u003C\/p\u003E\u003Cp\u003ELast year, he wrote a \u003Ca href=\u0022https:\/\/royalsocietypublishing.org\/doi\/10.1098\/rstb.2019.0372\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ereview of research\u003C\/a\u003E showing that people are very likely to sniff their hands subconsciously after a handshake, potentially to get a sense of the other person. This bizarre finding takes on a much greater importance during a time when handshakes are discouraged to prevent the spread of coronavirus.\u003C\/p\u003E\u003Cp\u003E\u2018We know that about 25% of viral transmission is through bringing your own hands to your face. That was an estimate before Covid. Thinking in evolutionary terms, if a behaviour persists despite a very high cost, it must also confer a significant advantage. There must be a very, very good reason to do it,\u2019 said Prof. Sobel.\u003C\/p\u003E\u003Cp\u003EHe has also collected what he believes to be the largest fear sweat collection in the world, with more than 1,000 body odour samples from first-time parachutists in the Israeli army. With this unique collection, he has been able to show that the smell of fear reduces people\u2019s performance in a trust-based task, while\u0026nbsp;people with autism spectrum disorder performed better.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u2018In mammals, the sensory system that underlies both emotion and social interaction is their sense of smell. Our big picture claim is that humans are largely like that as well,\u2019 said Prof. Sobel.\u003C\/p\u003E\u003Cp\u003E\u2018It is not a popular thing to say, but our view is that humans are olfactory animals \u2013 it shows up in every direction that we look.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the European Research Council. 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