#réinfection

  • Covid-19 : premier cas documenté de réinfection – Réalités Biomédicales
    https://www.lemonde.fr/blog/realitesbiomedicales/2020/08/28/covid-19-premier-cas-documente-de-reinfection

    Publié en ligne le 25 août 2020 dans la revue Clinical Infectious Diseases, ce cas clinique concerne un homme de 33 ans résidant à Hong Kong.La première infection par le SARS-CoV-2 avait entraîné une toux avec crachats, un mal de gorge, de la fièvre et des maux de tête pendant trois jours. Le diagnostic de Covid-19 avait été confirmé le 26 mars par un test salivaire PCR. Le patient avait été hospitalisé trois jours plus tard et était sorti de l’hôpital deux semaines plus tard après que deux tests PCR, réalisés par écouvillonnage nasopharyngé et oropharyngé, aient été négatifs. Les médecins ne disposent que d’un unique prélèvement sanguin provenant de la première infection. Il s’avère que la sérologie était toujours négative dix jours après le début des symptômes.Lors du second épisode infectieux, le patient était de retour à Hong Kong après avoir séjourné en Espagne et être passé par le Royaume-Uni. Réalisé à l’aéroport le 15 août à son retour à Hong Kong, le test salivaire s’était révélé positif.

    #Covid-19#migrant#migration#reinfection#sante#circulation#test#hongkong#espagne#grandebretagne

  • Four scenarios on how we might develop immunity to #Covid-19
    https://www.statnews.com/2020/08/25/four-scenarios-on-how-we-might-develop-immunity-to-covid-19

    As Menachery sees it, the possibilities for the future when it comes to Covid-19 and human immunity break down as follows: sterilizing immunity, functional immunity, waning immunity, and lost immunity.

    [...]

    “So far, anyway, the evidence supports functional immunity, but the only way to see how long that will last is to follow people over time and see if those responses diminish,” she said.

    “The idea there is that, yes, your antibodies might wane, but your memory responses aren’t absent,” said Menachery, noting that when a primed immune system re-encounters the virus, production of antibodies would kick into gear.

    Christian Drosten, who is another co-discoverer of SARS-1, describes a future that fits into this category.

    “I clearly expect lasting and relevant immunity that is almost sterilizing immunity against #SARS-2 in almost every person infected with SARS-2,” Drosten, director of the Institute of Virology at Berlin’s Charité University Hospital, said via email.

    “It may be possible to become infected again, without any change in the virus. The resulting infection will be mild or asymptomatic, with significantly lower levels of virus replication and onward #transmission.”

    Drosten’s last point would be a big bonus. If people who are reinfected don’t generate high levels of SARS-2 viruses in their respiratory tracts and therefore don’t contribute much to the spread of the virus, Covid-19 may become, over time, not just less dangerous, but also less common.

    “It may become a rare infection, although that is difficult to foresee given the size of the global population,” Koopmans said.

    Another hopeful part of this scenario relates to young children, who are far less likely than adults to develop severe disease. Krammer expects that children who first encounter the virus when they are very young may end up being infected several times over their lifetimes, but those later infections won’t lead to severe illness, even when they are elderly.

    #sars-cov2 #immunité #réinfection

  • #COVID-19 : des chercheurs disent avoir découvert un premier cas de #réinfection | JDM
    https://www.journaldemontreal.com/2020/08/24/covid-19-des-chercheurs-disent-avoir-decouvert-un-premier-cas-de-

    « Ce n’est pas un motif pour s’alarmer : cela illustre à merveille la façon dont l’#immunité devrait fonctionner », a quant à elle souligné sur Twitter la Dre Akiko Iwasaki, spécialiste de l’immunité à l’université Yale.

    « La seconde infection était asymptomatique. Si l’immunité n’a pas été suffisante pour empêcher la réinfection, elle a protégé cette personne contre la maladie », a-t-elle développé.

    « Puisqu’une réinfection peut se produire, il est improbable que l’immunité collective acquise par les infections naturelles suffise à éliminer le SARS-CoV-2 . La seule manière d’aboutir à une immunité collective est la #vaccination », a-t-elle conclu.

    • Coronavirus. Des cas de réinfection signalés en Belgique et aux Pays-Bas
      https://www.ouest-france.fr/sante/virus/coronavirus/coronavirus-des-cas-de-reinfection-signales-en-belgique-et-aux-pays-bas

      Pour confirmer qu’il s’agit d’une véritable recontamination, des tests génétiques sont nécessaires pour déterminer si la première et la seconde infection ont éventuellement été provoquées par des souches différentes du virus. Que des cas de réinfection émergent, cela ne m’inquiète pas, a souligné Marion Koopmans. Nous devons voir si cela arrive souvent, a-t-elle ajouté.

      Aucun commentaire n’a pu être obtenu dans l’immédiat auprès du ministère néerlandais de la Santé.

      « Ce n’est pas une bonne nouvelle »

      En ce qui concerne le patient belge, le virologue Marc Van Ranst a précisé à la télévision publique belge VRT qu’il s’agissait d’une femme ayant été contaminée une première fois en mars, puis une seconde fois en juin.

      Je pense que dans les prochains jours nous verrons d’autres histoires comparables […] Il pourrait s’agir d’exceptions, mais ces cas existent et il n’y en a pas qu’un, a-t-il dit en jugeant que ce n’est pas une bonne nouvelle.

      Marc Van Ranst a expliqué que, dans le cas de la patiente belge, qui présentait des symptômes légers de Covid-19, les anticorps développés après l’infection initiale pourraient être insuffisants pour prévenir une nouvelle contamination par une souche légèrement différente du virus mais pourraient malgré tout contribuer à limiter la sévérité des symptômes.

    • Covid-19 News: Live Updates - The New York Times
      A Nevada lab confirmed the first coronavirus reinfection in the U.S., a case that included severe symptoms.
      https://www.nytimes.com/2020/08/28/world/covid-19-coronavirus.html

      A public health laboratory in Nevada has reported the first confirmed coronavirus reinfection in the United States, and the first in the world known to have brought on severe symptoms.

      The first three confirmed reinfections in the world were reported this week, one in Hong Kong and two in Europe, all mild.

      Reinfection does not surprise researchers, given the millions of cases around the world, but it is not yet clear if such cases — particularly severe ones — are anomalies or will prove common.

      The patient is a 25-year-old man in Reno who apparently experienced a second bout of infection just 48 days after his first, according to health officials in Nevada.

      Experts have said that even low levels of antibodies and T cells in response to infection should last for a few months and provide some protection against the virus, which appears to have been borne out in the other confirmed reinfections.

      The patient in Nevada had a sore throat, cough, nausea and diarrhea starting on March 25. He tested positive on April 18, recovered by April 27, and tested negative twice. He began to feel unwell again on May 28, and three days later sought help for a similar set of symptoms.

      He was hospitalized on June 5 for shortness of breath and needed oxygen; an X-ray showed the “ground-glass opacities” typical of Covid-19.

      Researchers genetically sequenced the viruses from each bout, and found they were too different to be accounted for by an extended first illness. The findings have been submitted for consideration to the Lancet Infectious Diseases journal.

      Mark Pandori, the director of Nevada’s state lab, said it wasn’t clear why the second bout was more severe. “There may be a biological reason for that, but we can’t sure at this time,” he said.

      The researchers did not test the man for antibodies after the first illness, but found that he had them after the second.

      Some experts said the severe symptoms could mean that the patient had not developed antibodies after the first infection, or that his immune response was overpowered by a massive dose of virus the second time. It is also possible that he suffered antibody-dependent enhancement, in which the immune response may worsen symptoms on a second encounter.

      The findings highlight the need for widespread testing and viral sequencing, said Angela Rasmussen, a virologist at Columbia University in New York who was not involved in the work. “You really are going to need to look at a lot of these cases to try to start to narrow down which hypothesis is probably right,” she said.

    • Several have been reinfected with Covid-19. Here’s what that means
      https://www.statnews.com/2020/08/28/covid-19-reinfection-implications

      It’s possible that these early cases of reinfection are outliers and have features that won’t apply to the tens of millions of other people who have already shaken off Covid-19.

      [...]

      “The most important question for reinfection, with the most serious implications for controlling the pandemic, is whether reinfected people can transmit the virus to others,” Columbia University virologist Angela Rasmussen wrote in Slate this week.

      Unfortunately, neither the Hong Kong nor the Reno studies looked at this question. But if most people who get reinfected don’t spread the virus, that’s obviously good news.

      [...]

      A crucial question for which there is not an answer yet is whether what happened to the man in Reno, where the second case was more severe than the first, remains a rare occurrence, as researchers expect and hope. As the Nevada researchers wrote, “the generalizability of this finding is unknown.”