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  • #Forever_Chemicals Are Widespread in U.S. Drinking Water - Scientific American
    https://www.scientificamerican.com/article/forever-chemicals-are-widespread-in-u-s-drinking-water

    And Andrews and Naidenko’s study does not even fully capture Americans’ exposure to these chemicals because it only looks at two #PFAS compounds and one source. “We’re also being exposed to many more PFASs via the drinking water,” Wang says. The paper omitted other compounds because of a lack of widespread data, “but it means [the study offers] a conservative estimate of how we are being exposed to PFASs,” he adds. Higgins notes that people are also exposed to the compounds in substances besides drinking water, such as household products and food. “It’s a much broader exposure question,” he says. “Those other sources of exposure should not be ignored.”

    #eau #états-unis

  • A Flu Shot Might Reduce Coronavirus Infections, Early Research Suggests - Scientific American
    https://www.scientificamerican.com/article/a-flu-shot-might-reduce-coronavirus-infections-early-research-su

    There could be other explanations for the association the Radboud scientists and their colleagues found. For instance, people who choose to receive a flu shot may be more health-conscious and more likely to follow #COVID-19 prevention guidelines than individuals who do not get vaccinated. Netea agrees, noting that overall behavior, rather than the shot, might have made people in the former group less likely to get sick in his study.

  • How Straight Talk Helped One State Control #COVID - Scientific American
    https://www.scientificamerican.com/article/how-straight-talk-helped-one-state-control-covid

    ... late last year I heard about a cluster of fevers in December. And the chorus of warning voices grew between Christmas and New Year’s. As soon as we all returned from the New Year’s break on January 2 or 3, my office started to prepare. By February 8, we had distributed PPE [personal protective equipment] to nursing homes, hospitals and first responders. We had our contract tracing plan all mapped out. This was weeks ahead of our first documented case of COVID-19 on March 12.

    How important are testing and contact tracing to your response?

    They’re essential. Though we’ve had relatively few cases, we have 100 people tracing, and we have plans to hire more. Since May, we’ve partnered with a Maine-based laboratory, IDEXX, that has a very deep bench in reagents. So unlike some states, we’ve had no problems getting reagents for #tests. Everyone in the state 12 months or older can get tested at no cost, no questions asked.

    Do you think part of Maine’s success comes from its being relatively rural and remote?

    Not really. Other rural states such as Idaho, the Dakotas, West Virginia have much higher rates. That suggests that geography doesn’t have much explanatory power.

    What metrics do you rely on to measure success?

    Our goal is not to eradicate the disease but to suppress the virus to put us in a favorable position for vaccination. Our test positivity rate is consistently under 1 percent, and for weeks it [remained] under 0.6 percent. That’s the lowest in the U.S., and we think that puts us in a good position.

    What went wrong with the federal government’s response to the virus?

    It’s unclear…. We do know that on February 25, when [Nancy] Messonnier, [head of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases], warned Americans to prepare for a pandemic, she was threatened [with firing by President Donald Trump in a call to the Secretary of Health and Human Services, according to reporting by the Wall Street Journal], and the CDC started to take a back seat.

    What would be your first step in changing the federal response?

    Stop candy coating. The communication approach has been filtered through what folks in Washington, D.C., want the intended impact to be: it’s outcome driven, and that doesn’t work. They have to stop shaping the message to conform with what they think people want to believe.

    Can you a give concrete example of this distorted messaging?

    The rollout of [the antiviral] #remdesivir, as though it were “mission accomplished.” We actually knew very little at that time about whether the drug worked in the treatment of COVID-19. This happened with other therapies as well.

    You give regular press briefings on public radio, as well as daily interviews on Maine AM radio. What do you hope to accomplish with these frequent interactions with the press and public?

    All too often, government is on the defensive, and our first inclination is to say, ‘Here’s what [the government has] done; here’s what we need to do.’ But in a high-anxiety, low-trust situation like this, you have to empower people to act. Every five or six weeks, I take stock of where we are and come up with a couple of key asks of the people in Maine. For example, this week, I asked them to commit to get a flu shot. It’s a concrete call to action, something everyone can do for themselves and their family. And it builds confidence and trust.

    #Maine #etats-unis #responsable

  • Debunking the False Claim That COVID Death Counts Are Inflated - Scientific American
    https://www.scientificamerican.com/article/debunking-the-false-claim-that-covid-death-counts-are-inflated

    “When we ask if #COVID killed somebody, it means ‘Did they die sooner than they would have if they didn’t have the virus?’” Lessler says. Even such a person with a potentially life-shortening preexisting condition such as heart disease or diabetes may have lived another five, 10 or many more years, had they not become infected with #COVID-19.

  • What #COVID-19 #Reinfection Means for Vaccines - Scientific American
    https://www.scientificamerican.com/article/what-covid-19-reinfection-means-for-vaccines

    Thanks to months of intensive research, we now have a relatively clear picture of the antibody response triggered specifically by #SARS-CoV-2. Those who are asymptomatic produce low—sometimes even undetectable—levels of antibodies, even when the virus has been cleared. For the most part, studies show that concentrations of these antibodies diminish rapidly, suggesting that asymptomatic individuals may be the most susceptible to reinfection. Those who fall ill, and particularly those who fall seriously ill, produce greater amounts of antibodies that persist for longer amounts of time—an outcome that would seem, upon first glance , to offer greater protection, too.

    The Kenya study [https://academic.oup.com/jid/article/217/11/1728/4948258] on endemic human coronaviruses, however, offers evidence to the contrary that may turn out to be applicable to SARS-CoV-2. In some patients, it was found that high antibody levels actually potentiated infection rather than preventing or mitigating it—

    #immunité

  • Découverte d’anomalies immunologiques et génétiques associées à des formes sévères de #Covid-19 – Réalités Biomédicales
    https://www.lemonde.fr/blog/realitesbiomedicales/2020/09/27/decouverte-danomalies-immunologiques-et-genetiques-associees-a-des-formes-se

    La présence d’#auto-anticorps (IgG) dirigés contre au moins un #interféron de type I a été détectée chez 13,7 % des patients (135 sur 987) présentant une forme #critique de Covid-19. [...] Des auto-anticorps dirigés contre les interférons de type I ont également été détectés dans des échantillons de plasma sanguin prélevés chez des patients avant qu’ils aient développé la Covid-19, ce qui montre que la production des auto-anticorps n’a pas été déclenchée par l’infection par le #SARS-CoV-2.

    Les chercheurs [...] rapportent que 101 des 987 patients présentant une forme #sévère de Covid-19, soit chez 10,2 % d’entre eux, possèdent des auto-anticorps (IgG) capables de neutraliser au moins un interféron de type I.

    [...] En revanche, ces auto-anticorps n’ont été trouvés que chez 4 des 1227 sujets sains (0,3 %) et chez aucun des 663 patients présentant une infection asymptomatique ou modérée par le SARS-CoV-2.

    [...]

    Implications cliniques

    Tout d’abord, estiment les chercheurs, la détection des auto-anticorps dirigés contre les interférons de type I pourrait permettre d’identifier les patients infectés par le SARS-CoV-2 présentant un risque de développer une forme critique de la maladie Covid-19.

    Ensuite, en cas de guérison, le plasma de ces patients (pouvant contenir des auto-anticorps) ne devrait pas être utilisé dans le cadre des essais cliniques en cours visant à administrer le plasma de patients convalescents pour traiter des personnes atteintes de Covid-19 .

    Par ailleurs, ajoutent les auteurs, on peut imaginer d’utiliser des techniques permettant d’éliminer sélectivement les auto-anticorps ou les cellules qui les produisent***.

    Enfin, un traitement par interféron-bêta, par voie injectable ou inhalée, pourrait être bénéfique dans la mesure où il est rare que des patients porteurs d’auto-anticorps contre les IFN-I développent des auto-anticorps vis-à-vis de cette autre catégorie d’interférons, concluent-ils.

    [...]

    Défauts génétiques

    L’équipe franco-américaine, qui appartient au consortium international du COVID Human Genetic Effort, a publié dans Science un second article. Cette fois, les chercheurs ont recherché la présence d’anomalies sur des gènes responsables de la synthèse des interférons de type I chez des patients présentant une forme critique de Covid-19, faisant l’hypothèse [ en fait déjà vérifiée par d’autres auteurs ] que la sévérité de la maladie pouvait, chez certains patients, être imputable à ces variants génétiques. [...]

    Les chercheurs rapportent que 3,5 % des patients qui présentaient une forme critique de Covid-19 étaient porteurs d’une anomalie génétique affectant la réponse immunitaire dépendante des interférons de type I. De façon surprenante, ces défauts génétiques (dont certains peuvent être délétères en cas d’infection grippale) sont restés silencieux et n’ont pas eu d’impact clinique jusqu’au moment de l’infection par le SARS-CoV-2 [...]

    #immunité

    Auto-antibodies against type I IFNs in patients with life-threatening COVID-19 | Science
    https://science.sciencemag.org/content/early/2020/09/23/science.abd4585.full

    Inborn errors of type I IFN immunity in patients with life-threatening COVID-19 | Science
    https://science.sciencemag.org/content/early/2020/09/25/science.abd4570.full

    • One in Seven Dire COVID Cases May Result from a Faulty Immune Response - Scientific American
      https://www.scientificamerican.com/article/one-in-seven-dire-covid-cases-may-result-from-a-faulty-immune-re

      Perhaps the most immediate implication of the new studies concerns the use of convalescent plasma, an experimental treatment made from the blood of people who have recovered from COVID-19. In August the U.S. Food and Drug Administration issued a controversial “emergency use authorization” for the blood product. Zúñiga points out that it would be important to screen plasma donors for auto-antibodies. “If you have severe COVID-19, would you like to receive antibodies that neutralize an antiviral response?” she asks. “No thank you.”

      Given the growing evidence that interferon plays a crucial role in arresting severe infection, Fish believes that treating COVID-19 patients with interferon, regardless of their antibody or genetic status, could be a winning tactic, particularly early in the infection. She points to exploratory studies on interferon in Cuba and Wuhan, China, that showed promising effects on mortality rates and earlier clearance of the virus.

      But determining the #timing and other details of such treatment will be vital. “Interferon can be a double-edged sword in many infections,” Zúñiga says. “It activates many immune cells, but it can enhance inflammation as well. And it can have a negative immunoregulatory role, activating factors that suppress the immune response.”

      Experts seem to agree that interferons would have to be given early to help shut down the infection. Once a patient develops an extreme immune reaction sometimes called a “cytokine storm,” interferons are unlikely to be of use, Fish says.

      Dozens of COVID-19 clinical trials are already underway to test the efficacy of various types of interferon therapies, which can be given as a nasal spray or injection. One large study, conducted by the National Institute of Allergy and Infectious Diseases, is comparing the antiviral remdesivir alone with a combined therapy of the drug and interferon-beta. And Fish is involved in a study in Santiago, Chile, that will investigate whether giving interferons to members of a household where someone has been infected with the coronavirus could prevent them from falling ill. It remains to be seen whether any of these therapies pan out, but the new findings at least unlock one more piece of the COVID-19 puzzle.

  • For Math Fans: A Hitchhiker’s Guide to the Number 42 - Scientific American
    https://www.scientificamerican.com/article/for-math-fans-a-hitchhikers-guide-to-the-number-42

    Everyone loves unsolved mysteries. Examples include Amelia Earhart’s disappearance over the Pacific in 1937 and the daring escape of inmates Frank Morris and John and Clarence Anglin from Alcatraz Island in California in 1962. Moreover our interest holds even if the mystery is based on a joke. Take author Douglas Adams’s popular 1979 science-fiction novel The Hitchhiker’s Guide to the Galaxy, the first in a series of five. Toward the end of the book, the supercomputer Deep Thought reveals that the answer to the “Great Question” of “Life, the Universe and Everything” is “forty-two.”

    Deep Thought takes 7.5 million years to calculate the answer to the ultimate question. The characters tasked with getting that answer are disappointed because it is not very useful. Yet, as the computer points out, the question itself was vaguely formulated. To find the correct statement of the query whose answer is 42, the computer will have to build a new version of itself. That, too, will take time. The new version of the computer is Earth. To find out what happens next, you’ll have to read Adams’s books.

    The author’s choice of the number 42 has become a fixture of geek culture. It’s at the origin of a multitude of jokes and winks exchanged between initiates. If, for example, you ask your search engine variations of the question “What is the answer to everything?” it will most likely answer “42.” Try it in French or German. You’ll often get the same answer whether you use Google, Qwant, Wolfram Alpha (which specializes in calculating mathematical problems) or the chat bot Web app Cleverbot.
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    Since the first such school was created in France in 2013 there has been a proliferation of private computer-training institutions in the “42 Network,” whose name is a clear allusion to Adams’s novels. Today the founding company counts more than 15 campuses in its global network. The number 42 also appears in different forms in the film Spider-Man: Into the Spider-Verse. Many other references and allusions to it can be found, for example, in the Wikipedia entry for “42 (number).”

    The number 42 also turns up in a whole string of curious coincidences whose significance is probably not worth the effort to figure out. For example:

    In ancient Egyptian mythology, during the judgment of souls, the dead had to declare before 42 judges that they had not committed any of 42 sins.

    The marathon distance of 42.195 kilometers corresponds to the legend of how far the ancient Greek messenger Pheidippides traveled between Marathon and Athens to announce victory over the Persians in 490 B.C. (The fact that the kilometer had not yet been defined at that time only makes the connection all the more astonishing.)

    Ancient Tibet had 42 rulers. Nyatri Tsenpo, who reigned around 127 B.C., was the first. And Langdarma, who ruled from 836 to 842 A.D. (i.e., the 42nd year of the ninth century), was the last.

    An obvious question, which indeed has been asked, is whether the use of 42 in Adams’s books had any particular meaning for the author. His answer, posted in the online discussion group alt.fan.douglas-adams, was succinct: “It was a joke. It had to be a number, an ordinary, smallish number, and I chose that one. Binary representations, base thirteen, Tibetan monks are all complete nonsense. I sat at my desk, stared into the garden and thought ‘42 will do.’ I typed it out. End of story.”

    #42 #Geek_culture #Mathématiques

  • In an era of pandemics and climate change, we need to reconsider what “national security” means - Scientific American
    https://www.scientificamerican.com/article/its-time-to-rein-in-inflated-military-budgets

    Such a reassessment is long overdue. Despite the trillions of dollars Congress and successive administrations have lavished on the Pentagon since the turn of the century, the massive U.S. arsenal and fighting force deployed worldwide are powerless against grave, nonmilitary threats to national security—from a raging pandemic to the fact that tens of millions of Americans breathe foul air, drink tainted water, and struggle to pay for food, housing and health care.

    #milliers_de_milliards #états-unis #sécurité_nationale

  • How Could the Beirut Explosion Happen? Experts Explain - Scientific American
    https://www.scientificamerican.com/article/how-could-the-beirut-explosion-happen-experts-explain

    One thing we’ve been trying to be very careful about is not hypothesizing too early in the process. We don’t have a ton of information [for Beirut], but we’ve seen the videos of the explosion. Seeing the shock wave—it’s very rare to see that. What we’re talking about is that really thin, spherical white shape moving away from the explosion . What you’re actually seeing is water vapor condensing out of the air, because of really low pressure right behind the high-pressure shock wave. And then you can see it disappears right away, because it’s evaporating once the pressure equalizes. You can see the actual shock wave, so you know that it detonated—and only certain things can get you to a detonation.

    What do you mean by detonation?
    OGLE: A shock wave travels faster than the speed of sound, and that’s the hallmark of a detonation. There are two kinds of decomposition reactions that you can find in ammonium nitrate when it’s starting to build up enough pressure to cause damage. The first is called a deflagration. It’s a wave—literally a chemical reaction wave—that is traveling through the material slower than the speed of sound. As it continues to travel, it accelerates. And if it gets to the point where it hits the speed of sound, that’s what we call a detonation. A detonation yields far more damaging mechanisms against things such as structures and buildings.

    What else can you learn from the video footage from Beirut?
    SMYTH: A lot of the times when we’re analyzing video, we’re looking for the sequence and timing of events. When we’re investigating an explosion, there’s usually both explosion damage and fire damage. It’s always one of our goals to figure out: Was it fire, then explosion or explosion, then fire? The video we see that shows a fire before the explosion is really useful.
    OGLE: There’s a very distinctive reddish-brown cloud that’s rising up, following the explosion. It’s not the same thing as performing a chemical analysis, but [the cloud] is very distinctive and would be consistent with the decomposition products of ammonium nitrate—the primary one being nitrogen oxide. I think, at least visually, there’s a potential confirmation there that ammonium nitrate [is] participating in the overall reaction.

    What can cause ammonium nitrate to explode?
    OGLE: It’s stable under normal conditions, but you can do things to it that will cause it to misbehave. The main trigger is an external heat source. Depending on how you want to count it, there have been probably somewhere between 20 and 30 major catastrophic explosions with ammonium nitrate since it came on the scene as a commercial product in the 1920s. And fire is a frequent trigger. It’s the heat of the fire that warms up the ammonium nitrate that can become a problem. If it is heated by a large heat source like a fire, the ammonium nitrate will begin to decompose—and that decomposition can be mild and harmless, or it can be catastrophic.

    The difference between the two is whether or not the ammonium nitrate is pushed together in a stockpile. Think of it like a bonfire with a bunch of logs. When you build up that bonfire, those logs are trapping the heat, which accelerates the burning and makes the big fire. Whereas if you spread them out, the heat escapes to the atmosphere harmlessly. The same thing is true with the ammonium nitrate if it’s loaded up in, for example, what they call supersacks (these flexible containers that can [often] hold about one [metric] ton each). If you pile them up with no airflow in between, then any heat that gets generated during a decomposition is trapped and can’t get out. That heat raises the temperature and accelerates the decomposition, and there’s nothing to stop it.

    With the stockpile of ammonium nitrate in Beirut, what precautions should have been taken?
    OGLE: In the U.S., we turn to [a nonprofit] organization called the National Fire Protection Association to give us guidance on how to safely handle things like hazardous materials. If you exceed a threshold quantity of material—one half of a [metric] ton [of ammonium nitrate]—then you need to take a much more sophisticated approach to how you store and handle the material to keep it safe. If you have 2,750 [metric] tons, first and foremost, the thing you need to do is move that material far away from the population. It represents a significant hazard.

    When investigating an explosion, what other clues do you look for?
    SMYTH: The presence of a crater is another indication of the size of the explosion and what could potentially be involved. And the radii of damage: How far do you have minor structural damage? Broken windows? Major structural damage? Looking at how far away things are damaged can help you estimate how much power or energy or force was released. Those types of information can be used to back out what specifically happened. If you’re looking at a smaller explosion within a building, you can look for directional indications: where this wall was blown out toward the north and this wall was blown out toward the east. You can also look at fragments, missiles or shrapnel that were thrown during the explosion to both estimate how much force you’d need to move that fragment, as well as where they are coming from. Oftentimes we’re looking for fragments of certain pieces of equipment to put them back together like a puzzle: you might be able to look at those pieces and understand why they fragmented the way they did. Time lines are really important to our work. Understanding how long something was exposed to a fire, when someone was last in the room [and] noted that everything was normal, when people first see smoke—that type of [establishment of] a time line can be really helpful to help us [set bounds on] what’s going on, as well as potentially eliminate different hypotheses.

    OGLE: You’re searching for little nuggets of gold through a bunch of other kinds of fluff. But that requires interviews and searching through documents. One of the things, for example, that there’s been some talk about in the news media is whether or not there were any fireworks stored either nearby or, potentially, in the same warehouse [as the ammonium nitrate in Beirut]. Given the devastation that you’re looking at, it would be probably difficult to find physical evidence of that. You’re going to have to rely on people, and maybe documents, that will help you establish whether or not some materials were being stored in adjacent warehouses or in the same one.

    #Beyrouth #nitrate_d’ammonium #Liban

  • An Immune Protein Could Prevent Severe #COVID-19 -if It Is Given at the Right Time - Scientific American
    https://www.scientificamerican.com/article/an-immune-protein-could-prevent-severe-covid-19-if-it-is-given-a

    "... viruses are smart. They have several proteins that can antagonize and suppress early interferon responses.” One of SARS-CoV-2’s own defenders, a viral protein called Nsp1, can shut down the host cell’s production of immune molecules, including interferons, researchers in Munich reported on July 17 in Science.

    [..,]

    “if the interferon response begins before viral replication peaks, we will have protective immunity,” he says. If the viruses thwart this antiviral defense, however, the delayed interferon response becomes pathogenic—summoning too many monocytes, which secrete inflammatory molecules and cause tissue damage. “It’s the relative timing of interferon with virus replication that’s the key,” Channappanavar says.

    [...]

    Therapeutically, the findings suggest that #interferons matter in the initial phase of infection. “If you give interferon early, you can really increase the antiviral response. This is where you gain the most,” says Miriam Merad, who directs the Precision Immunology Institute at the Icahn School of Medicine at Mount Sinai and was not involved with the new research. If a person with COVID-19 has already progressed to having #inflammation, “and you go in and give interferon, you are going to make things worse,” she says. In an open-label preprint study in China, #interferon nasal drops prevented the disease in at-risk medical staff who had treated infected individuals. Early unpublished data from COVID-19 patients hospitalized in the U.K. suggest that interferons inhaled directly into the lungs shortened hospital stays and increased odds of recovery. And a randomized trial in Iran is testing whether the proteins can enhance a base therapeutic regimen in moderate to severe COVID-19 patients.

  • The Biggest Psychological Experiment in History Is Running Now - Scientific American
    https://www.scientificamerican.com/interactive/the-biggest-psychological-experiment-in-history-is-running-now

    Faced with potentially traumatic events, “about 65 percent of people are going to show minimal psychological symptoms,” says clinical psychologist George Bonanno of Teacher’s College at Columbia University. Bonanno, who is an expert on resiliency, studies the aftermath of hurricanes, terrorist attacks, life-threatening injuries and epidemics such as the 2003 SARS outbreak. His research and that of others consistently show three common psychological responses to hardship. Two thirds of people follow a resilience trajectory and maintain relatively stable psychological and physical health. About 25 percent struggle temporarily with psychopathology such as depression or post-traumatic stress disorder and then recover—a pattern known as the recovery trajectory. And 10 percent suffer lasting psychological distress. These results hold true across diverse populations and socioeconomic statuses. “We’re talking about everybody,” Bonanno says. On the other hand, the risk of psychiatric disorders is twice as high for people on the lowest economic rungs.

    But the mental health effects of a crisis so sweeping and insidious may not adhere to this paradigm.

    #mental #covid-19 #sars-cov2 #coronavirus

  • Psychological Trauma Is the Next Crisis for #Coronavirus Health Workers - Scientific American
    https://www.scientificamerican.com/article/psychological-trauma-is-the-next-crisis-for-coronavirus-health-w

    ... #burnout cannot capture what doctors, nurses, paramedics and others are experiencing as coronavirus overwhelms the health care system. “Burnout is a chronic response to health care conditions,” West says. “This is an unprecedented acute crisis.”

    #soignants #mental

  • How ’Superspreading’ Events Drive Most #COVID-19 Spread - Scientific American
    https://www.scientificamerican.com/article/how-ldquo-superspreading-rsquo-events-drive-most-covid-19-spread

    When describing how the #SARS-CoV-2 virus spreads, epidemiologists not only use the average number of other people that one individual infects but also employ another key value called the dispersion factor, or “k.” This number describes how much a disease clusters. A small k generally means that a relatively small number of cases are responsible for #transmissions, while a larger k indicates that transmissions are more evenly spread. In Hong Kong, researchers calculated that in more than 1,000 COVID-19 cases they examined, the value for k was 0.45. That value was higher than that of SARS or MERS—two previous viral outbreaks that featured superspreading—but much lower than that of the 1918 flu pandemic. In other words, SARS-CoV-2’s transmission is not as reliant on superspreading as SARs and MERS were but is far more dependent on it than influenza, Scarpino says.

    [...]

    The evidence about superspreadering activities has led researchers to believe they are responsible for much of the new coronavirus’s transmission. “All of the data I’m seeing so far suggest that if you tamp down the superspreader events, the growth rate of the infections stops very, very quickly,” Scarpino says. “We saw in Seattle that there were at least a couple of introductions that did not lead to new cases”—implying that the virus can fade out if it is denied circumstances for spreading.

    #Coronavirus : les « supercontamineurs », clé de la propagation de l’épidémie ?
    https://www.futura-sciences.com/sante/actualites/coronavirus-coronavirus-supercontamineurs-cle-propagation-epidemie-

    La plupart des épidémiologistes se concentrent sur le taux de reproduction (R0) qui définit le nombre moyen de personnes infectées par une personne malade. Ce taux est d’environ 1,5 pour la grippe, entre 1,5 et 3 pour le Sars-Cov-2, entre 10 et 12 pour la varicelle et jusqu’à 18 pour la rougeole. Mais cette moyenne est en fait très peu représentative de la réalité : « La norme, c’est que ce taux de reproduction est de zéro. La plupart des gens ne transmettent pas le virus », explique Jamie Lloyd-Smith, virologue à l’Université de Californie dans le magazine Science. Les scientifiques ont donc établi un autre indicateur, le #facteur_de_dispersion, noté #k. Plus k est petit, plus la propagation de la maladie s’effectue via un faible nombre de personnes.

    [...]

    Le Sars-Cov-2 semble particulièrement enclin à se propager à partir de #clusters.

  • #Téflon : les molécules #toxiques « s’incrustent partout, jusqu’aux tréfonds de l’#Arctique »
    https://reporterre.net/Teflon-les-molecules-toxiques-s-incrustent-partout-jusqu-aux-trefonds-de

    Un avocat devenu le pire cauchemar du puissant groupe chimique DuPont : telle est l’histoire — vraie — racontée dans Dark Waters. Le film étasunien, diffusé dans les cinémas français à partir du 26 février dernier et disponible depuis ce 19 mai en vidéo à la demande (VOD) en raison de la pandémie de Covid-19, met en scène Robert Bilott, un avocat spécialisé dans la défense des industries chimiques. Interpellé par un fermier dont le troupeau de vaches est décimé, il découvre que la campagne de son enfance est empoisonnée par une usine du groupe #DuPont, premier employeur de la région. L’avocat mène l’enquête et découvre que les eaux sont souillées par des rejets d’acide perfluoro-octanoïque (#PFOA), une substance utilisée pour produire le Téflon de nos poêles [1]. Pendant des années, Robert Bilott s’est battu pour mettre au jour les agissements de l’entreprise et a levé le voile sur un scandale sanitaire d’ampleur mondiale. Aujourd’hui, 99 % des habitants de la planète présentent des traces de cette molécule dans leur sang.

    ’Forever Chemicals’ Are Building Up in the Arctic—and Likely Worldwide - Scientific American
    https://www.scientificamerican.com/article/forever-chemicals-are-building-up-in-the-arctic-and-likely-world

    Cet article discute du fait de savoir s’ils sont dangereux ou pas... sans conclure.

    #Substances_alkylées_per_et_polyfluorées #eau #forever_chemicals

  • #COVID-19 : 28 millions de chirurgies annulées | santé log
    https://www.santelog.com/actualites/covid-19-28-millions-de-chirurgies-annulees

    En 12 semaines, COVID-19 aura entraîné l’annulation de 28 millions de chirurgies dans le monde, révèle cette étude d’épidémiologistes de l’Université de Birmingham, qui sensibilisent à l’arrêt global des procédures, mais aussi des parcours de soins de millions de patients, atteints de maladies chroniques. Autant de patients confrontés à une longue attente pour la résolution de leurs problèmes de santé, révèle cette étude, présentée dans le British Journal of Surgery.

    Ce qui a conduit certains à affirmer qu’une partie de la #surmortalité actuelle était due à cet « arrêt des procédures et parcours de soins » et, partant, que le taux de décès par #COVID-19 était surestimé,

    L’article ci-dessous est au contraire en faveur d’une sous-estimation des #décès par COVID_19 (ici aux #etats-unis).

    How COVID-19 Deaths Are Counted - Scientific American
    https://www.scientificamerican.com/article/how-covid-19-deaths-are-counted1

    Both undercounts and overcounts of COVID-19 deaths are possible, Wolfson said, but it’s not yet clear which is more likely, or whether they might simply balance each other out. Fowkes said that based on her experience, it’s more likely that COVID-19 deaths are being missed than overcounted. That’s because New York is among several cities that show spikes in deaths at home, and these anomalous spikes could be due to untested, untreated COVID-19. 

    Perhaps, the best clue as to whether COVID-19 deaths have been undercounted or overcounted is excess mortality data. Excess mortality is deaths above and beyond what would normally be expected in a given population in a given year. CDC data shows a spike of excess mortality in early 2020, adding up to tens of thousands of deaths.

    Some argue that many of these excess deaths are related to COVID-19 lockdowns, not COVID-19 themselves, Faust said, because people fear catching the disease if they go to the hospital for other reasons. A study in the Journal of the American College of Cardiology did find that nine major hospitals saw a 38% drop in emergency visits for a particular kind of heart attack in March. That suggests that people really are delaying or avoiding medical care, which could mean that some of them die of preventable causes. 

    But non-COVID conditions probably don’t explain most excess deaths, Faust said. Only a portion of heart attack visits would have represented lives saved, he said, because doctors must treat perhaps 10 patients to save one life. And other causes of death—such as motor vehicle accidents—are down.

    This could change with time, Faust cautioned. For example, if cancer patients forego their treatments for a year, rather than a few months, the impact on their death rates is much more likely to be noticeable in the population-wide data. But for now, he said, “it’s unlikely that the coronavirus deaths are being overcounted by a magnitude that explains our observation that something very unusual is going on.”

  • Comment le changement climatique va affecter notre #santé | AFD - Agence Française de Développement
    https://www.afd.fr/fr/actualites/comment-le-changement-climatique-va-affecter-notre-sante

    Despite Climate Change Health Threats, Few Medical Schools Teach It - Scientific American
    https://www.scientificamerican.com/article/despite-climate-change-health-threats-few-medical-schools-teach-

    Heat, mosquito-borne diseases and air pollution are medical issues that should be viewed through a climate lens, advocates say

    #climat #médecine

  • How NIST Tested Facial Recognition Algorithms for Racial Bias
    https://www.scientificamerican.com/article/how-nist-tested-facial-recognition-algorithms-for-racial-bias

    Some algorithms were up to 100 times better at identifying white faces Facial-recognition technology is already being used for applications ranging from unlocking phones to identifying potential criminals. Despite advances, it has still come under fire for racial bias : many algorithms that successfully identify white faces still fail to properly do so for people of color. Last week the National Institute of Standards and Technology (NIST) published a report showing how 189 (...)

    #algorithme #biométrie #racisme #facial #reconnaissance #discrimination