/articles

  • Severe #COVID-19 in the young and healthy: monogenic inborn errors of immunity? | Nature Reviews Immunology
    https://www.nature.com/articles/s41577-020-0373-7

    Severe COVID-19 is rare in previously healthy individuals who are less than 50 years of age, affecting probably no more than 1 in 1,000 such infected individuals. We suggest that these patients may become critically ill because of monogenic inborn errors that disrupt protective immunity to SARS-CoV-2.

    #génétique

  • 21 July — Viral levels could help to target treatment
    https://www.nature.com/articles/d41586-020-00502-w

    Onya Opota and his colleagues at Lausanne University Hospital analysed the viral load — the amount of virus in a standard volume of material — of samples taken from 4,172 people infected with SARS-CoV-2 between 1 February and 27 April (D. Jacot et al. Preprint at medRxiv http://doi.org/d4b8; 2020). They noticed two distinct stages of COVID-19. Early in the disease, people have high viral loads, which tend to decline gradually as the disease progresses. This later stage is typically characterized by inflammation. The decline of viral loads could thus serve as a cue to start treating infected people with anti-inflammatory drugs.

    But the researchers found no correlation between viral load and the severity of disease, suggesting that it is not a good predictor of a patient’s outcome. The research has not yet been peer reviewed.

  • Potent neutralizing antibodies directed to multiple epitopes on #SARS-CoV-2 spike | Nature
    https://www.nature.com/articles/s41586-020-2571-7

    ... we report the isolation of 61 SARS-CoV-2-neutralizing monoclonal antibodies from 5 infected patients hospitalized with severe disease. Among these are 19 antibodies that potently neutralized the authentic SARS-CoV-2 in vitro, 9 of which exhibited exquisite potency [...]

    [...]

    Several of these monoclonal antibodies are promising candidates for clinical development as potential therapeutic and/or prophylactic agents against SARS-CoV-2.

    #anticorps

  • #immunité_innée

    Le déficit en #Interférons de type 1 dans le sang : une signature pour détecter les patients à risque de forme sévère de #Covid-19 et une piste thérapeutique
    https://www.pasteur.fr/fr/espace-presse/documents-presse/deficit-interferons-type-1-sang-signature-detecter-patients-risque-forme-sev

    L’étude révèle par ailleurs que de faibles taux d’IFN de type 1 dans le plasma précèdent l’aggravation clinique des patients et leur transfert en soins intensifs. Les taux d’IFN de type 1 circulant caractériseraient même chaque stade de maladie, les taux les plus bas étant observés chez les patients les plus graves. Ces résultats suggèrent que dans l’infection à #SARS-CoV-2 la production de l’IFN de type I est freinée chez l’hôte infecté, ce qui pourrait expliquer les formes sévères plus fréquentes chez des individus faiblement producteurs de cette #cytokine, comme les personnes âgées ou ceux ayant des comorbidités.

    Par conséquent, la déficience en IFN de type I pourrait être une signature des formes graves de la COVID-19 et pourrait permettre d’identifier une population à haut risque.

    Ces résultats suggèrent en outre que l’administration d’IFN-alpha combinée avec une thérapie anti-inflammatoire ciblant l’IL-6 ou le TNF-α, ou des corticoïdes comme la #dexamethasone, chez les patients les plus sévères pourrait être une piste thérapeutique à évaluer pour enrayer les formes sévères de COVID-19.
     

    Source

    Impaired type I interferon activity and inflammatory responses in severe COVID-19 patients, Science, 13 juillet 2020

  • Chloroquine does not inhibit infection of human lung cells with SARS-CoV-2 | Nature
    https://www.nature.com/articles/s41586-020-2575-3

    Here, we show that engineered expression of TMPRSS2, a cellular protease that activates SARS-CoV-2 for entry into lung cells4, renders SARS-CoV-2 infection of Vero cells insensitive to chloroquine. Moreover, we report that chloroquine does not block SARS-CoV-2 infection of the TMPRSS2-positive lung cell line Calu-3. These results indicate that chloroquine targets a pathway for viral activation that is not operative in lung cells and is unlikely to protect against SARS-CoV-2 spread in and between patients.

  • Hydroxychloroquine use against SARS-CoV-2 infection in non-human primates | Nature
    https://www.nature.com/articles/s41586-020-2558-4

    We evaluated the antiviral activity of HCQ both in vitro and in SARS-CoV-2-infected macaques. HCQ showed antiviral activity in African green monkey kidney cells (VeroE6) but not in a model of reconstituted human airway epithelium. In macaques, we tested different treatment strategies in comparison to placebo, before and after peak viral load, alone or in combination with azithromycin (AZTH). Neither HCQ nor HCQ+AZTH showed a significant effect on the viral load levels in any of the tested compartments. When the drug was used as a pre-exposure prophylaxis (PrEP), HCQ did not confer protection against acquisition of infection. Our findings do not support the use of HCQ, either alone or in combination with AZTH, as an antiviral treatment for COVID-19 in humans.

  • Global #methane levels soar to record high
    https://www.nature.com/articles/d41586-020-02116-8

    Methane, an odourless gas, comes from several natural and anthropogenic sources. It is an important contributor to global warming because it traps heat in the atmosphere. It is also involved in ground-level formation of #ozone, which is an air pollutant and bad for human health.

    Methane’s atmospheric lifetime — around 12 years — is much shorter than that of carbon dioxide, which lingers for more than a century. But methane is, per unit, more than 20 times as potent as CO2 as a greenhouse gas. That means that over a 20-year period, the global-warming potential of one tonne of atmospheric methane is similar to that of around 85 tonnes of CO2, according to the Intergovernmental Panel on Climate Change. When looking at its impact over 100 years, one tonne of methane is still equivalent to about 28 tonnes of CO2.

    Roughly one-third of global methane emissions come from bacteria in natural wetlands that produce the gas when decomposing organic material. Agriculture and fossil-fuel sources each account for 20–25% of global methane emissions.

    The scientists found no evidence that emissions from wetlands or other natural sources had increased substantially from the 2000–06 average. But emissions from agriculture — driven by rising red meat consumption in some parts of the world — rose by almost 12%, to 227 million tonnes in 2017. Fossil fuels — including natural-gas fields and leaking pipelines — contributed 108 million tonnes of methane emissions in 2017, a rise of 17%.

    [...]

    The reports find that emissions have increased in most regions, and most markedly in Africa, the Middle East, China and South Asia. Europe is the only region where methane emissions seem to have dropped in recent years, thanks to declining cattle numbers and policy efforts to reduce emissions such as from landfills and manure.

    #climat

  • New Data on T Cells and the Coronavirus | In the Pipeline
    https://blogs.sciencemag.org/pipeline/archives/2020/07/15/new-data-on-t-cells-and-the-coronavirus

    A propos de :

    SARS-CoV-2-specific T cell immunity in cases of #COVID-19 and SARS, and uninfected controls | Nature
    https://www.nature.com/articles/s41586-020-2550-z

    Now comes a new paper in press at Nature. It confirms that convalescent patients from the current epidemic show T-cell responses (mostly CD4+ but some CD8+ as well) to various epitopes of the N (nucleocapsid) protein, which the earlier paper had identified as one of the main antigens as well (along with the Spike and M proteins, among others, with differences between the CD4+ and CD8+ responses as well).

    Turning to patients who had caught #SARS back in #2003 and recovered, it is already known (and worried about) that their antibody responses faded within two or three years. But this paper shows that these patients still have (17 years later!) a robust T-cell response to the original SARS coronavirus’s N protein, which extends an earlier report of such responses going out to 11 years. This new work finds that these cross-react with the new #SARS_CoV-2 N protein as well. This makes one think, as many have been wondering, that T-cell driven immunity is perhaps the way to reconcile the apparent paradox between (1) antibody responses that seem to be dropping week by week in convalescent patients but (2) few (if any) reliable reports of actual re-infection. That would be good news indeed.

    Et comme dans une étude précédente, il semble exister une #immunité croisée même chez les personnes qui n’ont jamais été en contact avec le sars-2003 ou le coronavirus du #MERS ; de plus une partie de cette dernière semble être due à un contact avec des coronavirus animaux.

  • Jeremy Farrar sur Twitter :
    “Antibodies may wane, that does not necessarily mean immunity is lost. We do not yet know correlate protection. A study that has always fascinated me-memory BCells from survivors 1918 Flu pandemic isolated >90 years later. Human immune system is remarkable” / Twitter
    https://twitter.com/JeremyFarrar/status/1283512382724030465

    Neutralizing antibodies derived from the B cells of 1918 influenza pandemic survivors | Nature
    https://www.nature.com/articles/nature07231

    #immunité #anticorps

  • Seule quasi-certitude, si transmission par #aérosol il y a, elle joue un rôle beaucoup plus grand dans les espaces clos, surtout sans présence de lumière du jour.

    Mounting evidence suggests #coronavirus is airborne — but health advice has not caught up
    https://www.nature.com/articles/d41586-020-02058-1

    Outside the lab, it is much more of a challenge to detect #aerosols and show that they can transmit the virus. In one study, researchers in Wuhan, China, detected #SARS-CoV-2 RNA in aerosol samples collected in a hospital9. But the WHO and others have criticized studies such as this because they detect only viral RNA, not infectious virus. “All these researchers are struggling to find the viable virus” in clinical settings, says Allegranzi. “Whenever this is found, it will be really very relevant.”

    One of the problems researchers face in studying virus viability in aerosols is the way that samples are collected. Typical devices that suck in air samples damage a virus’s delicate lipid envelope , says Julian Tang, a virologist at the University of Leicester, UK. “The lipid envelope will shear, and then we try and culture those viruses and get very, very low recovery,” he says.

    A few studies, however, have successfully measured the viability of aerosol-borne virus particles. A team at the US Department of Homeland Security Science & Technology Directorate in Washington DC found that environmental conditions play a big part in how long virus particles in aerosols remain viable. SARS-CoV-2 in mock saliva aerosols lost 90% of its viability in 6 minutes of exposure to summer sunlight, compared with 125 minutes in darkness 10. This study suggests that indoor environments might be especially risky, because they lack ultraviolet light and because the virus can become more concentrated than it would in outdoor spaces.

    Researchers say that one big unknown remains: how many virus particles are needed to trigger an infection? That’s one reason that Allegranzi would like to see randomized trials that demonstrate that interventions aimed at controlling aerosols actually work. One example, she says, would be a trial showing that tight-fitting respirator masks offer better protection than looser-fitting medical masks in a health-care setting.

    Tang, who contributed to the commentary, says the bar of proof is too high regarding airborne transmission. “[The WHO] ask for proof to show it’s airborne, knowing that it’s very hard to get proof that it’s airborne,” he says. “In fact, the airborne-transmission evidence is so good now, it’s much better than contact or droplet evidence for which they’re saying wash [your] hands to everybody.”

    #covid_19 #transmission

  • Don’t ask if artificial intelligence is good or fair, ask how it shifts power
    https://www.nature.com/articles/d41586-020-02003-2

    Law enforcement, marketers, hospitals and other bodies apply artificial intelligence (AI) to decide on matters such as who is profiled as a criminal, who is likely to buy what product at what price, who gets medical treatment and who gets hired. These entities increasingly monitor and predict our behaviour, often motivated by power and profits. It is not uncommon now for AI experts to ask whether an AI is ‘fair’ and ‘for good’. But ‘fair’ and ‘good’ are infinitely spacious words that any AI (...)

    #algorithme #police #racisme #données #prédiction #sexisme #bénéfices #biais #BigData #discrimination #LGBT #santé (...)

    ##santé ##surveillance

  • Pre-existing immunity to #SARS-CoV-2: the knowns and unknowns | Nature Reviews Immunology
    https://www.nature.com/articles/s41577-020-0389-z

    In conclusion, it is now established that SARS-CoV-2 pre-existing immune reactivity exists to some degree in the general population. It is hypothesized, but not yet proven, that this might be due to immunity to CCCs [‘common cold’ coronaviruses]. This might have implications for #COVID-19 disease severity, herd immunity and vaccine development, which still await to be addressed with actual data.

    #immunité #immunité_croisée #coronavirus

  • Des croisements anciens entre Polynésiens et Amérindiens mis en évidence par la génétique

    Des analyses ADN confortent l’hypothèse de l’anthropologue Thor Heyerdahl. Mais on ignore si des Amérindiens ont débarqué en Polynésie, ou si ce sont les Polynésiens qui ont « découvert » l’Amérique avant Christophe Colomb.

    Par Hervé Morin Publié, lemonde.fr, mercredi 8 juillet 2020

    En 1937, le jeune anthropologue norvégien Thor Heyerdahl et sa femme Liv débarquent à Fatu Hiva, une île des Marquises, pour leur voyage de noces. Le séjour du couple de Robinson se prolonge. Heyerdahl est fasciné par des légendes locales, selon lesquelles les occupants de l’île seraient venus du Soleil-Levant. Dix ans plus tard, il s’embarque depuis le Pérou sur un radeau de balsa, pour prouver qu’un tel voyage d’est en ouest est possible. Le 7 août 1947, après cent un jours de mer, lui et ses cinq coéquipiers s’échouent sur un atoll des Tuamotu, au terme de 7 000 km d’une navigation mouvementée, apportant une éclatante démonstration de la faisabilité d’une telle dérive.

    L’odyssée du Kon-Tiki deviendra mythique dans le grand public, mais jusqu’à ce jour, les cercles académiques continuent de débattre avec fièvre de l’hypothèse d’Heyerdahl. La théorie dominante étant que le Pacifique a progressivement été exploré et colonisé depuis l’Asie, par les « nomades de la mer » de la civilisation Lapita, sur une période courant de 1 500 avant J.-C. à la fin du XIVe siècle.

    Sans nier la prépondérance de cette ruée maritime vers l’est, une étude, publiée le 9 juillet dans Nature, appuie l’intuition initiale d’Heyerdahl. Elle compare les génomes de 807 individus issus de 17 îles du Pacifique et de 15 groupes amérindiens de la côte du Pacifique. Alexander Ioannidis, postdoctorant à l’université de Stanford, et ses collègues, mettent en évidence des croisements qui seraient survenus vers 1 200 après J.-C. entre Polynésiens et Améridiens, à une époque où les premiers étaient en pleine exploration des derniers confettis du Pacifique.

    Génétique, linguistique et botanique

    Heyerdahl aurait-il vu juste ? « Nous ne pouvons pas dire si les Polynésiens ont atteint les Amériques et sont repartis (avec une certaine ascendance amérindienne), ou si les Amérindiens se sont rendus en Polynésie, comme le croyait Heyerdahl, mais nous pouvons confirmer qu’il y a eu contact, comme il le pensait, répond Alexander Ioannidis. Cela signifie que les influences culturelles des Amérindiens ont pu se propager dans la lointaine Polynésie, comme le théorisait Heyerdahl. »

    L’analyse génétique conforte des indices d’une autre nature, qui mêlent linguistique et botanique. « D’autres chercheurs avaient noté que la patate douce, dont nous savons qu’elle était originaire des Amériques et qu’elle y était largement utilisée comme culture, est arrivée en Polynésie des siècles avant que les marins européens n’atteignent le Pacifique, rappelle Alexander Ioannidis. En outre, le nom de la patate douce, dans de nombreuses langues polynésiennes, kumara, ressemble au nom autochtone utilisé pour la désigner dans certaines langues du nord-ouest de l’Amérique du Sud. »

    N’est-il pas trop beau pour être vrai que le signal le plus fort d’un héritage génétique d’origine amérindienne – provenant des Zenu de Colombie – pointe vers Fatu Hiva, vers 1150 après J.-C., là même où Heyerdhal a été happé par les légendes insulaires ? « Ce n’est pas une coïncidence totale, puisque cette île a été incluse dans notre base de données en partie à cause de ces légendes, répond Alexander Ioannidis. Nous avons trouvé un signe de contact sur Fatu Hiva, là où nous avons cherché, mais il y a beaucoup d’autres îles des Marquises et des Tuamotu qui ne figurent pas dans notre base de données, si bien que nous ne pouvons donc pas dire avec certitude où le contact a eu lieu précisément. »

    La « marge d’approximation » de la génétique

    L’étude de Nature évoque la « possibilité intrigante » que les Amérindiens aient été les premiers à s’installer à Fatu Hiva, et que des navigateurs venus de l’ouest soient arrivés en second lieu. Mais l’alternative a la préférence d’Alexander Ioannidis : « Je pense qu’il est plus probable que des Polynésiens aient atteint les Amériques, étant donné leur technologie de voyage et leur capacité démontrée à parcourir des milliers de milles en haute mer, ce qu’ils faisaient avec succès, à cette époque, à la recherche de nouveaux territoires insulaires. » Un voyage de cette nature a été recréé en 1976 par l’expédition, d’Hawaï à Tahiti, du Hokulea, un bateau polynésien traditionnel, bien plus manœuvrant qu’un radeau de balsa.

    « Il est également possible que certains Amérindiens, qui disposaient de bateaux empruntant la route commerciale côtière de l’Equateur-Colombie vers la Méso-Amérique, aient dérivé dans l’océan Pacifique et, portés par les courants équatoriaux, aient atteint les Tuamotu, convient Alexander Ioannidis. C’est exactement là qu’Heyerdahl a débarqué lors de son voyage de dérive reconstitué avec le Kon-Tiki depuis l’Amérique du Sud. » Mais l’hypothèse d’une découverte précolombienne des Amériques par d’aventureux Polynésiens reste pour lui plus convaincante.

    « Le sujet est vraiment fascinant ! », commente Vincent Lebot (Cirad) qui, en 2013, avait dirigé une étude génétique sur la diffusion de la patate douce dans le Pacifique, laquelle appuyait déjà fortement l’hypothèse de transferts du tubercule depuis l’Amérique du Sud (région du Pérou et de l’Equateur) vers la Polynésie. Il estime que la méthodologie et les marqueurs génétiques décrits dans Nature sont « suffisamment solides pour révéler des échanges entre deux populations qui étaient, à cette époque, suffisamment distantes génétiquement. » Lui aussi penche pour l’hypothèse d’un aller-retour de Polynésiens en Amérique, qui « auraient ramené avec eux des femmes ou des marins amérindiens ». Il note cependant que la génétique laisse « une marge d’approximation » concernant la datation de ces échanges, et salue le fait que les auteurs eux-mêmes mentionnent les limites de leur modèle.

    Héritage génétique indéchiffrable

    Jusqu’alors, l’hypothèse d’une origine amérindienne des Polynésiens avait été essentiellement testée sur les habitants de l’île de Pâques (les Rapa Nui), précisément parce qu’elle est la plus proche du continent américain (3 525 km des côtes chiliennes, tout de même), et distante de plus de 2 000 km de Pitcairn, la première île habitée vers l’ouest. L’héritage génétique de ses habitants était particulièrement indéchiffrable, du fait d’échanges, au XIXe siècle, avec des navigateurs d’origines européenne et amérindienne (peuples chiliens précolombiens). Les analyses ADN apportaient des résultats contradictoires sur une influence amérindienne antérieure.

    Une indécision tranchée par l’étude de Nature : « La composante amérindienne préhistorique sur Rapa Nui, sur laquelle tant de recherches ont porté, est probablement issue d’un événement de contact non pas sur Rapa Nui, mais quelque part en amont dans le processus de colonisation polynésienne des îles du Pacifique », y lit-on. L’arrivée d’ADN amérindien sur l’île de Pâques est datée de 1380.

    Combien d’individus ont-ils été impliqués dans ces croisements dont la trace génétique ténue s’est conservée et diffusée si largement dans l’immensité du Pacifique ? « Nous ne pouvons pas le dire, mais nous pouvons dire que l’ascendance amérindienne sur les différentes îles étudiées a été héritée des mêmes ancêtres, répond Alexander Ioannidis. Tous les ancêtres amérindiens préeuropéens proviennent également de la même région du nord de l’Amérique du Sud et datent d’à peu près la même époque. Cela nous amène à penser qu’une seule expédition a permis d’apporter ces ancêtres sur une île de la Polynésie orientale. Puis, lorsque les dernières îles polynésiennes éloignées ont été colonisées (comme l’île de Pâques), cette trace ancestrale a été portée vers ces nouveaux territoires avec les nouveaux colons, dans leur ADN désormais combiné. »

    « La nouvelle étude de Ionnidis et al. est passionnante et les résultats sont très convaincants, estime le paléogénéticien Lars Fehren-Schmitz (Université de Californie, à Santa Cruz), qui avait pourtant publié, en 2017, une étude excluant tout apport génétique amérindien avant l’arrivée des Européens sur l’île de Pâques. L’idée de déplacer l’attention de Rapa Nui vers d’autres communautés de Polynésie orientale me paraît logique, étant donné que même l’expérience de Thor Heyerdahl ne l’a pas conduit à Rapa Nui. Je suis particulièrement enthousiaste quant à leur hypothèse selon laquelle un flux génétique pourrait provenir de groupes vivant dans le nord de l’Amérique du Sud-Amérique centrale. »

    Pour lui, la preuve la plus convaincante de l’ascendance amérindienne chez des individus des communautés insulaires viendra, in fine, de l’analyse d’ADN ancien prélevé sur des squelettes datant de l’époque préeuropéenne. « Mais c’est aux communautés de ces îles de décider si cette question les intéresse », conclut-il.

    Hervé Morin

    https://www.lemonde.fr/sciences/article/2020/07/08/des-croisements-anciens-entre-polynesiens-et-amerindiens-mis-en-evidence-par

    #anthropologie #génétique #Amérindiens #Amérique #Polynésie #Pacifique

  • A guide to R — the pandemic’s misunderstood metric
    https://www.nature.com/articles/d41586-020-02009-w

    An important aspect of Rt is that it represents only an average across a region. This average can miss regional clusters of infection. Conversely, high incidences of infection among a spatially distinct smaller subsection of a population can sway a larger region’s Rt value. For instance, Germany’s national Rt value jumped from just over 1 to 2.88 in late June (later revised down to 2.17) largely because of an outbreak in a meat-processing plant at Gütersloh in North Rhine-Westphalia (see ’Germany’s Regional Outbreaks’). The Robert Koch Institute noted that national infections overall were still low, which is why the local outbreak had such an effect on the country’s Rt, which had dropped below 1 again by the end of June. This makes it unlikely that Rt would be used to steer local lockdown policy in Germany, Schaade says. “If the rolling mean of R was at 1.2 for a few weeks, then that would show there was a problem that needed attention, even if case numbers were low.” But in practice, researchers find out about local outbreaks before that because of a reported spike in cases, not because of changes to Rt. Germany has ongoing surveillance and public reporting of transmission levels in 400 counties.

    #épidémiologie

  • What’s the nature of immunity [to SARS-CoV-2] and how long does it last?
    https://www.nature.com/articles/d41586-020-01989-z

    Immunologists are working feverishly to determine what immunity to #SARS-CoV-2 could look like, and how long it might last. Much of the effort has focused on ‘neutralizing antibodies’, which bind to viral proteins and directly prevent infection. Studies have found2 that levels of neutralizing antibodies against SARS-CoV-2 remain high for a few weeks after infection, but then typically begin to wane.

    However, these antibodies might linger at high levels for longer in people who had particularly severe infections. “The more virus, the more antibodies, and the longer they will last,” says immunologist George Kassiotis of the Francis Crick Institute in London. Similar patterns have been seen with other viral infections, including SARS (severe acute respiratory syndrome). Most people who had SARS lost their neutralizing antibodies after the first few years. But those who had it really severely still had antibodies when re-tested 12 years later, says Kassiotis.

    Researchers don’t yet know what level of neutralizing antibodies is needed to fight off reinfection by SARS-CoV-2, or at least to reduce #COVID-19 symptoms in a second illness. And other antibodies might be important for immunity. Virologist Andrés Finzi of the University of Montreal in Canada, for example, plans to study the role of antibodies that bind to infected cells and mark them for execution by immune cells — a process called antibody-dependent cellular cytotoxicity — in responses to SARS-CoV-2.

    Ultimately, a full picture of SARS-CoV-2 immunity is likely to extend beyond antibodies. Other immune cells called T cells are important for long-term immunity, and studies suggest that they are also being called to arms by SARS-CoV-23,4. “People are equating antibody to immunity, but the immune system is such a wonderful machine,” says Finzi. “It is so much more complex than just antibodies alone.”

    Because there is not yet a clear, measurable marker in the body that correlates with long-term immunity, researchers must piece together the patchwork of immune responses and compare it with responses to infections with other viruses to estimate how durable protection might be. Studies5 of other coronaviruses suggest that ‘sterilizing immunity’, which prevents infection, might last for only a matter of months. But protective immunity, which can prevent or ease symptoms, could last longer than that, says Shane Crotty, a virologist at the La Jolla Institute of Immunology in California.

    #immunité #anticorps

  • Pourquoi le #Pôle Sud se réchauffe-t-il 3 fois plus vite que le reste de la planète ?
    https://www.numerama.com/sciences/634075-pourquoi-le-pole-sud-se-rechauffe-t-il-3-fois-plus-vite-que-le-rest

    Cette région de la planète est [...] constamment soumise à des fluctuations dans ses températures. Les auteurs de l’étude parue dans Nature Climate Change expliquent que ces changements extrêmes de température toutes les quelques décennies ont tendance à masquer l’impact total des activités humaines sur cette région. Mais cet impact est bien présent : le changement climatique semble intensifier l’ampleur des fluctuations naturelles du Pôle Sud, et donc accroître son réchauffement.

    #climat

  • The biggest mystery: what it will take to trace the coronavirus source
    https://www.nature.com/articles/d41586-020-01541-z

    The lab does hold coronaviruses related to SARS-CoV-2, so it is possible that one could have escaped, perhaps if a lab worker accidentally became infected from a virus sample or animal in the facility and then passed it on to someone outside the facility. It is also theoretically possible that scientists at the lab tweaked the virus’s genome for research purposes before it escaped, but, again, there is no evidence that they did. Shi declined to respond to Nature’s questions about her experiments, saying that she has been inundated with media requests.

    #Laboratoire_P4

  • Ethical guidelines for COVID-19 tracing apps
    https://www.nature.com/articles/d41586-020-01578-0

    Protect privacy, equality and fairness in digital contact tracing with these key questions. Technologies to rapidly alert people when they have been in contact with someone carrying the coronavirus SARS-CoV-2 are part of a strategy to bring the pandemic under control. Currently, at least 47 contact-tracing apps are available globally (see go.nature.com/2zc1qhk). They are already in use in Australia, South Korea and Singapore, for instance. And many other governments are testing or (...)

    #Apple #Google #algorithme #Alipay #Bluetooth #COVIDSafe_ #QRcode #SafeEntry #smartphone #contactTracing #géolocalisation #technologisme #consentement #métadonnées #obsolescence #BigData #COVID-19 #FreeSoftware #santé #selfie #surveillance #TraceTogether (...)

    ##santé ##AlipayHealthCode ##Smittestopp ##éthique

  • Clinical and immunological assessment of asymptomatic .#SARS-CoV-2 infections | Nature Medicine
    https://www.nature.com/articles/s41591-020-0965-6

    You May Have Antibodies After #Coronavirus Infection. But Not for Long. - The New York Times
    https://www.nytimes.com/2020/06/18/health/coronavirus-antibodies.html

    It’s a question that has haunted scientists since the pandemic began: Does everyone infected with the virus produce antibodies — and if so, how long do they last?

    Not very long, suggests a new study published Thursday in Nature Medicine. Antibodies — protective proteins made in response to an infection — may last only two to three months, especially in people who never showed symptoms while they were infected.

    The conclusion does not necessarily mean that these people can be infected a second time, several experts cautioned. Even low levels of powerful neutralizing antibodies may still be protective, as are the immune system’s T cells and B cells.

    But the results offer a strong note of caution against the idea of “immunity certificates” for people who have recovered from the illness, the authors suggested.

    Coronavirus : pour les malades sans symptômes, l’#immunité [humorale] face au #Covid-19 pourrait être plus faible - Sud Ouest.fr
    https://www.sudouest.fr/2020/06/18/coronavirus-pour-les-malades-sans-symptomes-l-immunite-face-au-covid-19-pou

    Huit semaines après la sortie de l’hôpital, les niveaux d’#anticorps neutralisants, qui confèrent a priori une immunité contre le virus, avaient diminué chez 81,1% des patients sans symptômes, contre 62,2% chez les patients symptomatiques.

    #asymptomatiques

    • A second paper, published on Thursday in the journal Nature, suggests that even low levels of antibodies might be enough to thwart the virus. “It does appear that even low levels of certain antibodies have potent neutralizing capability,” said Dr. Rasmussen, the Columbia University virologist. “Low antibody titers don’t necessarily determine whether a patient will be protected from reinfection.”

    • Thoughts on Antibody Persistence and the Pandemic | In the Pipeline
      https://blogs.sciencemag.org/pipeline/archives/2020/06/22/thoughts-on-antibody-persistence-and-the-pandemic

      ... when you hear of patients who are infected but are showing no symptoms, you could have a mental picture of a stronger immune response that’s keeping the virus knocked down more. But it’s clearly not that simple: this paper shows that the asymptomatic patients had a weaker antibody response that tended to disappear during the convalescent phase. That’s the result that’s gotten a lot of attention – as it should – although it’s important to not run with it too quickly. Remember, there is more than one type of immune response – you have T cells pitching in as well. That response is one of the great unanswered questions of the epidemic, from what I can see.

      [...]

      Everyone will have seen the various population surveys with antibody testing that have suggested, in most cases, that a rather small percentage of people have been exposed. Think of the various ways you could get such a result: (1) it’s just what it looks like, and most people are unprotected because they have so far been unexposed. (2) the antibody results are what they look like – low exposure – but people’s T-cell responses mean that there are actually more people protected than we realize. (3) the antibody results are deceiving, because (as this latest paper seems to show) the antibody response fades over time, meaning that more people have been exposed than it looks like. And that means you can split that into (3a) the antibody response fades, but the T-cell response is still protective and (3b) the antibody response fades and so does the T-cell response. That last one is not a happy possibility.

      You can extend this thinking to the effects of the coming vaccines.

    • In a new study published in the journal Nature, a team of astronomers finally found this missing mass with distant radio signals known as fast radio bursts, or FRBs. The amount of matter they detected was exactly consistent with what cosmologists predicted we’d find more than two decades ago. 

      Soon after FRBs were discovered in 2007, however, astronomers realized their potential as probes of this faint region of the Universe. While we still don’t understand exactly what FRBs are or how they’re emitted, we do know that most of them originate outside of the Milky Way and travel through vast reaches of interstellar space — including the WHIM — to reach telescopes here on Earth.

      Radio signals slow down as they pass through matter, with longer radio waves being slowed down more than shorter ones — a phenomenon known as “dispersion.” By measuring the amount of dispersion in a sample of FRBs, the team was able to determine just how much matter there really was hidden away within the WHIM.

      It only took 6 FRBs to weigh the Universe, but telescopes around the world are detecting more of these signals every day. Future observations will allow astronomers to map out how subatomic particles are distributed throughout the WHIM, shedding further light on one of the most mysterious regions of the cosmos.

    • A census of baryons in the Universe from localized fast radio bursts | Nature
      https://www.nature.com/articles/s41586-020-2300-2


      Fig. 1: Locations of FRBs relative to their host galaxies.

      °Abstract°
      More than three-quarters of the baryonic content of the Universe resides in a highly diffuse state that is difficult to detect, with only a small fraction directly observed in galaxies and galaxy clusters. Censuses of the nearby Universe have used absorption line spectroscopy to observe the ‘invisible’ baryons, but these measurements rely on large and uncertain corrections and are insensitive to most of the Universe’s volume and probably most of its mass. In particular, quasar spectroscopy is sensitive either to the very small amounts of hydrogen that exist in the atomic state, or to highly ionized and enriched gas in denser regions near galaxies. Other techniques to observe these invisible baryons also have limitations; Sunyaev–Zel’dovich analyses can provide evidence from gas within filamentary structures, and studies of X-ray emission are most sensitive to gas near galaxy clusters.

      Here we report a measurement of the baryon content of the Universe using the dispersion of a sample of localized fast radio bursts; this technique determines the electron column density along each line of sight and accounts for every ionized baryon. We augment the sample of reported arcsecond-localized fast radio bursts with four new localizations in host galaxies that have measured redshifts of 0.291, 0.118, 0.378 and 0.522. This completes a sample sufficiently large to account for dispersion variations along the lines of sight and in the host-galaxy environments11, and we derive a cosmic baryon density of 𝛺b=0.051 [+0.021,−0.025] ℎ^−1 / 70 (95 per cent confidence; h70 = H0/(70 km s^−1 Mpc^−1) and H0 is Hubble’s constant).

      This independent measurement is consistent with values derived from the cosmic microwave background and from Big Bang nucleosynthesis.


      Fig. 3: The density of cosmic baryons derived from the FRB sample

      The probability distribution of DMcosmic due to the cosmic baryons, p(DM), in semi-analytic models and simulations, as encoded in black, blue, red and green in order of increasing redshift (z; see key), is compared to the analytic form used in our analysis (DM; equation (4))..