• Early Release - Analysis of Asymptomatic and Presymptomatic Transmission in SARS-CoV-2 Outbreak, Germany, 2020 - Volume 27, Number 4—April 2021 - Emerging Infectious Diseases journal - CDC
    https://wwwnc.cdc.gov/eid/article/27/4/20-4576_article

    In this cluster of COVID-19 cases, little to no transmission occurred from asymptomatic case-patients [0 cas en fait]. Presymptomatic #transmission was more frequent [75%] than symptomatic transmission. The serial interval was short [incubation médiane : 4,3 jours] ; very short intervals occurred.

    [...]

    In conclusion, our study suggests that asymptomatic cases are unlikely to contribute substantially to the spread of #SARS-CoV-2. #COVID-19 cases should be detected and managed early to quarantine close contacts immediately and prevent presymptomatic #transmissions.

    #asymptomatiques #asymptomatique

  • 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.