Up 「外国人入国停止」──ポピュリズム政治の迷走 作成: 2020-12-28
更新: 2020-12-28

      読売新聞, 2020-12-27
    全世界の外国人 入国停止へ
     政府はお日、新型コロナウイルスの世界的な感染拡大を受け、全世界からの外国人の新規入国を今月28日から1月末まで停止すると発表した。 コロナ変異種が拡大する英国と南アフリカからの新規入国はすでに止めていたが、対象を全ての国・地域に広げる。 海外からの帰国者に対しても、ホテルや自宅での14日の待機措置を命じる。
     政府は現在、一部の国を除き、海外からの新規入国を原則として禁止している。 ただ、往来緩和策の一環として10月から、留学生や駐在員など在留資格を持つ外国人の入国を条件付きで例外的に認めていた。


    考えるとは,5W1H (what, when, where, who, why, how) の考え方をすることだが,ひとはこれができない。



    ( 「対策ゼロなら40万人死亡」)


      Cross Validated, 2020-12-22
    70% in the media
       Prime Minister Boris Johnson told a Downing Street briefing that early analysis showed the new strain could increase the reproductive rate by 0.4 or more and that it may be up to 70% more transmissible than the old variant.
    Recently the news has been covered with articles about a new strain of ncov-19 that is more contagious.
    It is said that it is "70% more transmissible".
    Where does this statistic come from?
    How has it been derived/estimated (from what raw data)
    and what does it mean statistically (accuracy, certainty)?

    The figure of 70% originates from a presentation by Dr. Erik Volz from Emperical College London.
    See the COG-UK showcase event on youtube

    2:36:41 – 2:46:50 Epidemiology of SARS-CoV-2 Genetic Variants. Dr Erik Volz, Imperial College London

    • What does more 'infectious' really mean?
      This model relates to a parameter called the selective advantage.
      In the SIR model paradigm this selective advantage is a ratio of reproduction rates, as explained in Gordo et.al. "Genetic Diversity in the SIR Model of Pathogen Evolution" PLoS ONE 4(3): e4876. (Of course, selective advantage can also occur differently in many different ways, for instance when the reproductive rate is the same or even lower but the incubation time is shorter)

    • On what measurements is it based?
      The raw data are measurements of occurances of the strain, and based on that estimates are made for the relative presence of the strain, or also the odds ratio for the probability that a randomly selected infection is of the specific strain.

    • How is it estimated?
      Based on a time series of this odds ratio an estimate is made for the relative growth rate and the selective advantage.
      This 70% means: that every 7 days (probably the used serial or generation interval in the computations) the relative presence of the new strain grows by a factor exp(0.7) ≈ 2

      In the presentation the used formula is
      (in the graphs it seems like log odds changes 4 units in a bit more than 1 month and probably they use ≈ 7 days) you get s = 0.7

      But that is an indirect representation of infectious/transmissibility.
      It is the relative difference in growth rates, it is not the relative infectiousness (e.g. relative reproduction rates).

      In addition to the meaning of the statistic being unclear, we also have issues with randomness and bias due to the way of sampling.
      Small fluctuations locally and in time can make a particular strain grow fast while being unrelated to the selective advantage. The measurements of the presence of the strain may not need to come from the same population but they are sampled from a wider group (e.g. it is measured in a hospital or a village, but possibly the growth is large in a particular part of the hospital or a particular neighborhood, and this might correlate with the strain. The growth is turbulent and noisy, and when the time-scale for the analysis is short then there might be a large chance to pick up a temporal fluctuation)

      So the 70% figure that had been presented by Boris Johnson, which is the relative growth rate of the new virus strain, is not the relative infectiousness.

    The 70% figure is more like a sidenote in the presentation.
    It was used to show that this strain grows relatively fast in the initial growth phase (and in other strains it is shown that this eventually decreases so this initial figure does not reflect the true relative infectiousness).
    It was not meant to be an estimate for the relative infectiousness.