Roques Lionel, Klein Etienne K, Papaïx Julien, Sar Antoine, Soubeyrand Samuel
INRAE, BioSP, 84914 Avignon, France.
Medicentre Moutier, 2740 Moutier, Switzerland.
Biology (Basel). 2020 May 8;9(5):97. doi: 10.3390/biology9050097.
The number of screening tests carried out in France and the methodology used to target the patients tested do not allow for a direct computation of the actual number of cases and the infection fatality ratio (IFR). The main objective of this work is to estimate the actual number of people infected with COVID-19 and to deduce the IFR during the observation window in France. We develop a `mechanistic-statistical' approach coupling a SIR epidemiological model describing the unobserved epidemiological dynamics, a probabilistic model describing the data acquisition process and a statistical inference method. The actual number of infected cases in France is probably higher than the observations: we find here a factor ×8 (95%-CI: 5-12) which leads to an IFR in France of 0.5% (95%-CI: 0.3-0.8) based on hospital death counting data. Adjusting for the number of deaths in nursing homes, we obtain an IFR of 0.8% (95%-CI: 0.45-1.25). This IFR is consistent with previous findings in China (0.66%) and in the UK (0.9%) and lower than the value previously computed on the Diamond Princess cruse ship data (1.3%).
在法国进行的筛查测试数量以及用于确定受测患者的方法，无法直接计算实际病例数和感染致死率（IFR）。这项工作的主要目标是估计法国在观察期内感染新冠病毒的实际人数，并推算出感染致死率。我们开发了一种“机械 - 统计”方法，该方法结合了一个描述未观察到的流行病学动态的SIR流行病学模型、一个描述数据采集过程的概率模型以及一种统计推断方法。法国的实际感染病例数可能高于观察到的数量：我们在此发现一个8倍的系数（95%置信区间：5 - 12），基于医院死亡计数数据，这导致法国的感染致死率为0.5%（95%置信区间：0.3 - 0.8）。对养老院死亡人数进行调整后，我们得出的感染致死率为0.8%（95%置信区间：0.45 - 1.25）。这个感染致死率与中国先前的研究结果（0.66%）和英国的研究结果（0.9%）一致，且低于之前根据钻石公主号邮轮数据计算出的值（1.3%）。
