Covid-19 : pourquoi Omicron semble moins sévère que le variant Delta

Les études scientifiques se multiplient depuis la fin de l’année 2021 pour confirmer que le variant Omicron du Sars-CoV-2 provoque moins de formes graves de la maladie que le Delta. Ces recherches donnent aussi des clés pour comprendre pourquoi cette souche s’attaque moins aux poumons.

Études après études, les scientifiques semblent confirmer l’impression que le variant Omicron entraîne des formes moins sévères du Covid-19 que la souche Delta. Depuis le 23 décembre, il y a même eu quatre publications allant dans le même sens : plus grande transmissibilité du virus, mais moins dangereux que Delta.

Des chercheurs de l’université de Liverpool ont conclu, dans un article mis en ligne le 26 décembre, que des souris contaminées par le variant Omicron perdaient moins de poids et avaient des formes moins sévères de pneumonie que des souris soumises à d’autres mutations du Sars-CoV-2.

Des hamsters dorés, utilisés par des scientifiques de l’université de Louvain (Belgique), ont eu une réaction similaire aux rongeurs de Liverpool, dans les résultats publiés également le 26 décembre d’une autre expérience pour évaluer la dangerosité du variant détecté en novembre 2021.

Loin des voies respiratoires inférieures

Des travaux de chercheurs américains soumis quelques jours avant la fin de l’année à la revue scientifique Nature et que le Guardian a pu consulter confirment que les souris contaminées par le variant Omicron ont des formes moins graves du Covid-19. Enfin, les données britanniques de fin décembre “démontrent qu’une personne affectée par le variant Omicron semble avoir entre 50 % et 70 % moins de risques d’être hospitalisée”, souligne Ian Jones, virologue à l’université de Reading, contacté par France 24.

“On peut donc dire que d’un point de vue épidémiologique, c’est un variant qui est moins sévère que le précédent”, conclut Björn Meyers, virologue à la faculté de médecine de l’université de Magdebourg, joint par France 24. “Il semble y avoir non seulement moins de cas d’hospitalisation, mais les personnes qui sont admises restent aussi moins longtemps et avec des symptômes moins forts”, ajoute Lawrence Young, virologue et professeur d’oncologie moléculaire à la Warwick Medical School, contacté par France 24.

Les nouvelles études scientifiques suggèrent aussi que cette apparente moindre sévérité d’Omicron aurait à voir avec la manière dont le virus infecte les cellules dans le corps humain. “Il emprunte la même porte pour entrer dans la cellule mais sans utiliser la même clé”, résume Lawrence Young de manière métaphorique.

Omicron s’accroche toujours à la cellule avec sa fameuse protéine Spike, mais les nombreuses mutations sur cette partie du virus font qu’il préfère se multiplier au niveau du nez, de la gorge et des bronches, sans s’aventurer autant vers les poumons comme c’était le cas avec les précédentes souches du Sars-CoV-2.

Cette différence primordiale lui permet d’être plus résistant aux vaccins, tout en étant potentiellement moins dangereux car “dans toutes les maladies respiratoires, le risque pour la santé est plus important quand le virus s’attaque aux voies respiratoires inférieures, comme les poumons. C’est ce qui se passe avec les agents de la grippe aviaire H5N1 qui viennent se loger au niveau des voies respiratoires inférieures”, explique Ian Jones, de l’université de Reading. 

Début de la phase endémique ?

“C’est probablement pourquoi on a affaire à un virus qui entraîne des formes moins sévères de la maladie tout en étant plus transmissible puisqu’il y a une plus forte concentration virale au niveau du nez et de la gorge, ce qui augmente le risque de contamination”, résume Jonathan Stoye, virologue et responsable de recherche au Francis Crick Institute de Londres, contacté par France 24.

Mais pour cet expert, il ne faut pas non plus surestimer la baisse de dangerosité d’Omicron. “On constate qu’il se multiplie plus facilement et plus vite au niveau des voies respiratoires supérieures que les souches précédentes, et il y aura toujours une proportion d’agents pathogènes qui vont finir par trouver leur chemin vers les poumons. C’est là que la vaccination est importante car elle permet de limiter le risque de contracter des formes graves du Covid-19”, précise ce spécialiste. 

“S’il est vrai qu’il semble être moins ‘sévère’ que le variant Delta, Omicron apparaît tout de même plus dangereux que le variant Alpha [dominant dans une partie de l’Europe à la fin de 2020, NDLR] dont il est un descendant plus direct”, précise, quant à lui, Björn Meyer, le virologue de l’université de Magdebourg.

ll y a donc deux manières de considérer Omicron. D’un côté, c’est une forme plus grave que son ancêtre – Alpha –, mais de l’autre, il apparaît plus bénin que le variant Delta qu’il est en train de supplanter au niveau mondial. Et d’un point de vue sanitaire, c’est ce dernier aspect qui importe aux yeux d’Ian Jones, car “c’est peut-être avec ce variant que l’on est entré dans la phase endémique de l’épidémie [c’est-à-dire que la maladie s’enracine, mais dans des formes plus anodines pour la santé, NDLR].”

“Ce serait en tout cas en phase avec ce que nous savons de l’histoire des coronavirus”, reconnaît Jonathan Stoye, le responsable de recherche au Francis Crick Institute de Londres. Certains précédents – comme la pandémie de grippe Russe de 1889 – suggèrent que ces virus ont tendance à commencer à s’atténuer au bout de deux ans environ. 

Là encore, “c’est logique d’un point de vue évolutionnaire, puisque les variants qui vont s’imposer sont ceux qui sont les plus contagieux, c’est-à-dire ceux qui sont plutôt présents dans les voies respiratoires supérieures, là où ils sont généralement moins dangereux pour la santé”, résume Ian Jones. En clair, une sorte de darwinisme viral pourrait donner un coup de pouce à l’effort vaccinal pour surmonter la pandémie.

En attendant, le propagation fulgurante d’Omicron contribue à mettre le système de santé sous forte pression. Car même si le variant est moins virulent, les hôpitaux doivent “gérer un fort absentéisme au quotidien [du personnel soignant] lié à la rapide progression des contaminations avec l’arrivée d’Omicron”, explique à France 24 

source:France24FR

134 thoughts on “Covid-19 : pourquoi Omicron semble moins sévère que le variant Delta

  1. Hey There. I found your blog using msn. This is a really
    well written article. I’ll be sure to bookmark it and come back to read more of your useful information.
    Thanks for the post. I will definitely comeback.

  2. We’re a group of volunteers and opening a new scheme in our community.
    Your site offered us with useful info to work on.
    You’ve performed a formidable process and our whole group can be thankful
    to you.

  3. Great blog! Do you have any recommendations for aspiring writers?

    I’m hoping to start my own website soon but I’m a little lost
    on everything. Would you recommend starting with a free platform like WordPress or
    go for a paid option? There are so many
    options out there that I’m completely confused
    .. Any recommendations? Cheers!

  4. Write more, thats all I have to say. Literally, it seems as
    though you relied on the video to make your point. You clearly know what
    youre talking about, why waste your intelligence on just posting videos to your blog when you could be giving us something enlightening to read?

  5. Everything is very open with a clear clarification of the challenges.
    It was truly informative. Your website is very helpful.
    Many thanks for sharing!

  6. Good day! Do you know if they make any plugins to protect against hackers? I’m kinda paranoid about losing everything I’ve worked hard on. Any suggestions?

  7. You really make it appear so easy together with your presentation but I to find this topic to be really something which I think I’d never understand. It sort of feels too complex and extremely wide for me. I am looking forward to your next post, I will try to get the dangle of it!

  8. Hi, I think your site might be having browser compatibility issues. When I look at your website in Safari, it looks fine but when opening in Internet Explorer, it has some overlapping. I just wanted to give you a quick heads up! Other then that, fantastic blog!

  9. Hey! Do you know if they make any plugins to
    safeguard against hackers? I’m kinda paranoid about losing everything
    I’ve worked hard on. Any suggestions?

  10. I’m not that much of a online reader to be honest but your sites really nice, keep it up!

    I’ll go ahead and bookmark your website to come back later on. Many thanks

  11. Does your site have a contact page? I’m having trouble locating it but, I’d like to send you an e-mail. I’ve got some recommendations for your blog you might be interested in hearing. Either way, great website and I look forward to seeing it grow over time.

  12. Just desire to say your article is as astounding. The clarity for your put up is
    just cool and that i could think you’re knowledgeable on this subject.
    Fine together with your permission allow me to snatch your feed to keep up to date with drawing close post.
    Thanks 1,000,000 and please keep up the
    gratifying work.

  13. This design is spectacular! You most certainly know how to keep a reader amused.
    Between your wit and your videos, I was almost moved to start my own blog (well,
    almost…HaHa!) Wonderful job. I really enjoyed what you had
    to say, and more than that, how you presented it.
    Too cool!

  14. Neat blog! Is your theme custom made or did you download
    it from somewhere? A theme like yours with a few simple tweeks would really make
    my blog shine. Please let me know where you got your design. Many thanks

  15. It’s a pity you don’t have a donate button! I’d most certainly donate to this fantastic blog!
    I guess for now i’ll settle for book-marking and adding your RSS
    feed to my Google account. I look forward to fresh updates and will talk
    about this site with my Facebook group. Chat soon!

  16. I’m really enjoying the design and layout of
    your blog. It’s a very easy on the eyes which makes it much more pleasant for me to come here and visit more often. Did you hire out a designer to create your theme?
    Exceptional work!

  17. Unquestionably believe that which you said. Your favorite reason seemed
    to be on the web the easiest thing to be aware of.
    I say to you, I certainly get annoyed while people think about worries that they just do not know about.
    You managed to hit the nail upon the top as well as
    defined out the whole thing without having side-effects , people can take a
    signal. Will likely be back to get more. Thanks

  18. Thanks for sharing excellent informations. Your web-site is very cool. I am impressed by the details that you have on this site. It reveals how nicely you perceive this subject. Bookmarked this website page, will come back for more articles. You, my friend, ROCK! I found simply the information I already searched everywhere and just couldn’t come across. What an ideal web site.

  19. I know this if off topic but I’m looking into starting my own weblog and was curious what all is needed to get set up? I’m assuming having a blog like yours would cost a pretty penny? I’m not very web savvy so I’m not 100 positive. Any tips or advice would be greatly appreciated. Appreciate it

  20. Hi would you mind stating which blog platform you’re working with?
    I’m going to start my own blog soon but I’m having a tough time choosing between BlogEngine/Wordpress/B2evolution and Drupal.
    The reason I ask is because your design and style seems different then most blogs and I’m looking for something completely unique.

    P.S Apologies for being off-topic but I had to ask!

  21. Hello There. I found your blog using msn. This is a
    really well written article. I will make sure to bookmark it and come back to
    read more of your useful information. Thanks for the post.
    I will certainly return.

  22. Someone essentially help to make seriously posts I’d state.
    That is the very first time I frequented your web page and up
    to now? I surprised with the analysis you made to create this actual submit incredible.
    Great task!

  23. Excellent read, I just passed this onto a colleague who was doing some research on that. And he just bought me lunch because I found it for him smile Therefore let me rephrase that: Thank you for lunch!

  24. I don’t even know how I ended up here, but I thought this post was good. I don’t know who you are but certainly you are going to a famous blogger if you are not already 😉 Cheers!

  25. I am really impressed with your writing skills as well as with the layout on your weblog. Is this a paid theme or did you customize it yourself? Anyway keep up the excellent quality writing, it is rare to see a nice blog like this one nowadays..

  26. magnificent points altogether, you simply received a new reader. What could you suggest about your publish that you simply made a few days in the past? Any positive?

  27. I’m really impressed with your writing skills as well as with the layout on your blog. Is this a paid theme or did you customize it yourself? Anyway keep up the excellent quality writing, it’s rare to see a great blog like this one these days..

  28. I intended to send you that tiny observation to be able to thank you as before for your personal precious tactics you have contributed in this case. It is quite incredibly open-handed of you in giving publicly exactly what many of us could have marketed for an ebook in order to make some money on their own, notably since you could possibly have done it if you ever decided. The tactics also worked like the fantastic way to comprehend other people have a similar eagerness like my personal own to figure out very much more related to this condition. I’m sure there are some more fun occasions up front for individuals that looked at your blog post.

  29. Hey there would you mind sharing which blog platform you’re working with? I’m planning to start my own blog in the near future but I’m having a tough time deciding between BlogEngine/Wordpress/B2evolution and Drupal. The reason I ask is because your design seems different then most blogs and I’m looking for something completely unique. P.S My apologies for getting off-topic but I had to ask!

  30. Simply wish to say your article is as surprising. The clarity in your post is simply great and i could assume you’re an expert on this subject. Fine with your permission allow me to grab your RSS feed to keep updated with forthcoming post. Thanks a million and please carry on the rewarding work.

  31. I really like your blog.. very nice colors & theme. Did you create this website yourself or did you hire someone to do it for you? Plz reply as I’m looking to create my own blog and would like to know where u got this from. appreciate it

  32. Hello! Someone in my Myspace group shared this website with us so I came to check it out. I’m definitely enjoying the information. I’m book-marking and will be tweeting this to my followers! Outstanding blog and wonderful design and style.

  33. Magnificent website. Lots of helpful information here. I am sending it to several friends ans additionally sharing in delicious. And obviously, thank you on your sweat!

  34. Hello my loved one! I want to say that this post is awesome, nice written and come with approximately all vital infos. I?¦d like to peer more posts like this .

  35. Thank you for the sensible critique. Me and my neighbor were just preparing to do some research on this. We got a grab a book from our area library but I think I learned more clear from this post. I am very glad to see such magnificent info being shared freely out there.

  36. Thanks for every other informative site. Where else may just I am getting that type of information written in such an ideal means? I’ve a undertaking that I’m just now working on, and I have been at the look out for such info.

  37. Have you ever considered writing an ebook or guest authoring on other sites? I have a blog based on the same information you discuss and would really like to have you share some stories/information. I know my subscribers would appreciate your work. If you are even remotely interested, feel free to shoot me an e-mail.

  38. You made some respectable points there. I looked on the web for the problem and found most people will go together with with your website.

  39. A formidable share, I simply given this onto a colleague who was doing a little bit analysis on this. And he in truth bought me breakfast as a result of I found it for him.. smile. So let me reword that: Thnx for the deal with! But yeah Thnkx for spending the time to debate this, I really feel strongly about it and love studying extra on this topic. If possible, as you turn into experience, would you mind updating your weblog with extra details? It is highly useful for me. Massive thumb up for this blog post!

  40. Admiring the dedication you put into your site and in depth information you provide. It’s awesome to come across a blog every once in a while that isn’t the same out of date rehashed material. Fantastic read! I’ve bookmarked your site and I’m adding your RSS feeds to my Google account.

  41. obviously like your web-site but you need to check the spelling on quite a few of your posts. A number of them are rife with spelling problems and I find it very bothersome to tell the truth nevertheless I’ll definitely come back again.

  42. You have noted very interesting details! ps nice web site. “‘Tis a sharp medicine, but it will cure all that ails you. — last words before his beheadding” by Sir Walter Raleigh.

  43. I would like to thnkx for the efforts you have put in writing this site. I am hoping the same high-grade blog post from you in the upcoming also. In fact your creative writing abilities has inspired me to get my own site now. Actually the blogging is spreading its wings rapidly. Your write up is a great example of it.

  44. Hi, Neat post. There’s a problem together with your web site in web explorer, might test this?K IE still is the market leader and a big section of other people will pass over your wonderful writing because of this problem.

  45. I have read some excellent stuff here. Definitely worth bookmarking for revisiting. I surprise how so much effort you put to make any such fantastic informative website.

  46. I have been surfing on-line more than 3 hours lately, but I by no means found any fascinating article like yours. It’s pretty price sufficient for me. In my view, if all website owners and bloggers made just right content as you probably did, the net might be much more useful than ever before.

  47. I’m no longer certain the place you’re getting your info, however great topic. I needs to spend some time studying much more or understanding more. Thank you for great information I was looking for this information for my mission.

  48. Lottery Defeater Software: What is it? Lottery Defeater Software is a completely automated plug-and-play lottery-winning software. The Lottery Defeater software was developed by Kenneth.

  49. What Is Neotonics? Neotonics is a skin and gut supplement made of 500 million units of probiotics and 9 potent natural ingredients to support optimal gut function and provide healthy skin.

  50. I was just looking for this info for some time. After 6 hours of continuous Googleing, at last I got it in your website. I wonder what’s the lack of Google strategy that do not rank this type of informative web sites in top of the list. Normally the top websites are full of garbage.

  51. Thanks , I’ve recently been looking for info approximately this topic for a while and yours is the best I have discovered till now. But, what in regards to the conclusion? Are you certain in regards to the source?

  52. We’re a group of volunteers and opening a brand new scheme in our community. Your website offered us with useful information to work on. You’ve performed an impressive task and our entire group will probably be thankful to you.

  53. Hi! This is my first visit to your blog! We are a group of volunteers and starting a new initiative in a community in the same niche. Your blog provided us useful information to work on. You have done a marvellous job!

  54. I am now not certain the place you are getting your info, but good topic. I needs to spend some time finding out much more or understanding more. Thank you for wonderful info I used to be looking for this info for my mission.

  55. whoah this weblog is wonderful i really like reading your articles. Stay up the great work! You already know, many persons are hunting round for this info, you could aid them greatly.

  56. The next time I read a blog, I hope that it doesnt disappoint me as much as this one. I mean, I know it was my choice to read, but I actually thought youd have something interesting to say. All I hear is a bunch of whining about something that you could fix if you werent too busy looking for attention.

  57. Fantastic goods from you, man. I have take into accout your stuff previous to and you are simply too wonderful. I really like what you have bought here, certainly like what you are saying and the way in which wherein you say it. You make it entertaining and you still care for to keep it sensible. I can’t wait to read far more from you. That is actually a great site.

  58. What i do not realize is in reality how you’re not really much more smartly-preferred than you might be now. You’re so intelligent. You already know therefore considerably with regards to this subject, produced me individually believe it from a lot of varied angles. Its like men and women aren’t involved except it?¦s something to accomplish with Lady gaga! Your own stuffs excellent. All the time handle it up!

  59. I’ll right away grasp your rss as I can’t to find your e-mail subscription link or newsletter service. Do you’ve any? Please allow me recognise in order that I may subscribe. Thanks.

  60. Hey very nice web site!! Man .. Excellent .. Amazing .. I’ll bookmark your web site and take the feeds also…I am happy to find so many useful information here in the post, we need work out more strategies in this regard, thanks for sharing. . . . . .

Leave a Reply

Your email address will not be published. Required fields are marked *