• Past SARS-CoV-2 Infection Mostly Protects Survivors | The Scientist Magazine®
    https://www.the-scientist.com/news-opinion/past-sars-cov-2-infection-mostly-protects-survivors-68358

    A large study of UK healthcare workers finds that immunity after coronavirus infection lasts for months, but those with antibodies may still be able to carry and spread the virus upon reexposure.

    Immune responses from a previous SARS-CoV-2 infection reduce survivors’ risk of reinfection by more than 83 percent for at least five months, according to preliminary data from a study of more than 20,000 UK healthcare workers published by Public Health England. The researchers caution that people previously infected may still be able to transmit the virus.

    “Overall I think this is good news,” Imperial College London epidemiologist Susan Hopkins, a senior medical adviser to Public Health England (PHE), tells The Guardian. “It allows people to feel that prior infection will protect them from future infections, but at the same time it is not complete protection, and therefore they still need to be careful when they are out and about.”

    Between June and November last year, the researchers monitored, through monthly serological tests and PCR tests twice a month, the infection rates in those who had been infected with the virus before June and those who had not. They found 44 potential reinfections, including 13 symptomatic cases, among the 6,614 who’d had the virus before, and 318 cases among the 14,173 who had no evidence of past infection. The authors concluded from these results that prior exposure to SARS-CoV-2 provides 94 percent protection against symptomatic reinfection, and 75 percent protection against asymptomatic reinfection.

    See “More SARS-CoV-2 Reinfections Reported, But Still a Rare Event”

    The researchers also found that people who become reinfected can carry a high viral load in their noses and throats, even in asymptomatic cases, which correlates with a higher risk of spreading the virus to others, says Hopkins.

    #porteurs_sains #covid-19 #réinfection

  • #SARS-CoV-2 #Transmission From People Without COVID-19 Symptoms | Infectious Diseases | JAMA Network Open | JAMA Network
    https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774707

    Results 
    The baseline assumptions for the model were that peak infectiousness occurred at the median of symptom onset and that 30% of individuals with infection never develop symptoms and are 75% as infectious as those who do develop symptoms. Combined, these baseline assumptions imply that persons with infection who never develop symptoms may account for approximately 24% of all transmission. In this base case, 59% of all transmission came from asymptomatic transmission, comprising 35% from presymptomatic individuals and 24% from individuals who never develop symptoms. Under a broad range of values for each of these assumptions, at least 50% of new SARS-CoV-2 infections was estimated to have originated from exposure to individuals with infection but without symptoms.

    Conclusions and Relevance
    In this decision analytical model of multiple scenarios of proportions of asymptomatic individuals with COVID-19 and infectious periods, transmission from asymptomatic individuals was estimated to account for more than half of all transmissions. In addition to identification and isolation of persons with symptomatic COVID-19, effective control of spread will require reducing the risk of transmission from people with infection who do not have symptoms. These findings suggest that measures such as wearing masks, hand hygiene, social distancing, and strategic testing of people who are not ill will be foundational to slowing the spread of COVID-19 until safe and effective vaccines are available and widely used.

    #asymptomatique

    • On savait que c’était majoritaire, ils se risquent à des estimations chiffrées. Ce qui peut aider à mieux faire piger ce point central à ces sceptiques qui croient ne croire que ce qu’ils voient (et regardent pas mal de vidéos déglinguantes comme on peut en trouver ici même ) : une majorité des contaminations est le fait de « porteurs sains » (au moins au moment où elles ont lieu), et avec lui l’autre aspect central : c’est le plus indiscernable, l’aérosolisation qui cause la majorité des contaminations. J’ai étoilé car je compte utiliser l’article de cette façon... (rien de glorieux, le côté pédago avec de la répétition - limite bourrage de crânes- des analogies, par exemple le VIH, et ce qu’il faut de variation pour par sombrer dans le désintérêt)

      Si il s’agit d’une lutte commune, encore faut-il que les (des) notions et contraintes de base soient connues. La compétence politique des n’importe qui en dépend. Nous en sommes loin.

      #contamination #porteurs_sains