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  1. Last 7 days
    1. Asymptomatic spread of coronavirus is ‘very rare,’ WHO says

      The claim is that, according to the WHO, asymptomatic spread of coronavirus is ‘very rare’. This statement is attributed to WHO official Dr. Maria Van Kerkhove during a recent news conference. It deserves greater clarification from the WHO, but Dr. Van Kerkhove appears to make the distinction between “asymptomatic” and “pre-symptomatic” individuals during her comments. This distinction is essential for proper interpretation of her statement. “Asymptomatic” refers to persons who test positive, but who never display symptoms throughout the course of their SARS-CoV-2 infection. In contrast, “presymptomatic” individuals are those with confirmed infection, who do not currently display symptoms, but later go on to develop COVID-19 related symptoms (fever, cough, loss of taste/smell, etc).

      Importantly, the distinction between asymptomatic and presymptomatic can only be made retrospectively. From a clinical standpoint, if someone currently has no symptoms, but tests positive, there is no way of knowing at that time if they are “asymptomatic” or “presymptomatic”. Preliminary data estimates that around 20% of SARS-CoV-2 infections are truly “asymptomatic”.

      If “asymptomatic” individuals were rarely involved in transmission of the virus, this would be an important finding, but from a practical standpoint if “presymptomatic” individuals still spread the virus (as the data indicates), then the rationale for preventative measures still stands. Early studies [1] [2] have estimated that up to 40-60% of virus spread occurs when people don’t have symptoms. Preventative measures such as social distancing and universal mask wearing have been implemented to prevent the spread of virus from individuals not currently demonstrating symptoms.

      Bottom line: Dr. Van Kerkhove appeared to refer to only “asymptomatic” individuals and not “presymptomatic” individuals in her statement. Clarification from the WHO, and public availability of the data leading to the claim, is needed for proper interpretation. At the current time, existing published data indicates that a significant amount of SARS-CoV-2 infections are due to individuals who did not have symptoms when they spread the virus.

    1. Corbett, K. S., Edwards, D., Leist, S. R., Abiona, O. M., Boyoglu-Barnum, S., Gillespie, R. A., Himansu, S., Schäfer, A., Ziwawo, C. T., DiPiazza, A. T., Dinnon, K. H., Elbashir, S. M., Shaw, C. A., Woods, A., Fritch, E. J., Martinez, D. R., Bock, K. W., Minai, M., Nagata, B. M., … Graham, B. S. (2020). SARS-CoV-2 mRNA Vaccine Development Enabled by Prototype Pathogen Preparedness. BioRxiv, 2020.06.11.145920. https://doi.org/10.1101/2020.06.11.145920

    1. Fontanet, A., Tondeur, L., Madec, Y., Grant, R., Besombes, C., Jolly, N., Pellerin, S. F., Ungeheuer, M.-N., Cailleau, I., Kuhmel, L., Temmam, S., Huon, C., Chen, K.-Y., Crescenzo, B., Munier, S., Demeret, C., Grzelak, L., Staropoli, I., Bruel, T., … Hoen, B. (2020). Cluster of COVID-19 in northern France: A retrospective closed cohort study. MedRxiv, 2020.04.18.20071134. https://doi.org/10.1101/2020.04.18.20071134

  2. Jul 2020
    1. Lavezzo, E., Franchin, E., Ciavarella, C., Cuomo-Dannenburg, G., Barzon, L., Del Vecchio, C., Rossi, L., Manganelli, R., Loregian, A., Navarin, N., Abate, D., Sciro, M., Merigliano, S., De Canale, E., Vanuzzo, M. C., Besutti, V., Saluzzo, F., Onelia, F., Pacenti, M., … Crisanti, A. (2020). Suppression of a SARS-CoV-2 outbreak in the Italian municipality of Vo’. Nature, 1–1. https://doi.org/10.1038/s41586-020-2488-1

  3. Jun 2020
    1. Li, Z., Chen, Q., Feng, L., Rodewald, L., Xia, Y., Yu, H., Zhang, R., An, Z., Yin, W., Chen, W., Qin, Y., Peng, Z., Zhang, T., Ni, D., Cui, J., Wang, Q., Yang, X., Zhang, M., Ren, X., … Li, S. (2020). Active case finding with case management: The key to tackling the COVID-19 pandemic. The Lancet, 0(0). https://doi.org/10.1016/S0140-6736(20)31278-2

    1. Ferguson, N., Laydon, D., Nedjati Gilani, G., Imai, N., Ainslie, K., Baguelin, M., Bhatia, S., Boonyasiri, A., Cucunuba Perez, Z., Cuomo-Dannenburg, G., Dighe, A., Dorigatti, I., Fu, H., Gaythorpe, K., Green, W., Hamlet, A., Hinsley, W., Okell, L., Van Elsland, S., … Ghani, A. (2020). Report 9: Impact of non-pharmaceutical interventions (NPIs) to reduce COVID19 mortality and healthcare demand. In 20 [Report]. https://doi.org/10.25561/77482

    1. Hsiang, S., Allen, D., Annan-Phan, S., Bell, K., Bolliger, I., Chong, T., Druckenmiller, H., Huang, L. Y., Hultgren, A., Krasovich, E., Lau, P., Lee, J., Rolf, E., Tseng, J., & Wu, T. (2020). The effect of large-scale anti-contagion policies on the COVID-19 pandemic. Nature, 1–9. https://doi.org/10.1038/s41586-020-2404-8