Department of Mechanical Engineering, Texas Tech University, Lubbock, TX, United States of America.
PLoS One. 2022 Aug 17;17(8):e0268332. doi: 10.1371/journal.pone.0268332. eCollection 2022.
Motivated by several possible differences in Covid-19 virus strains, age demographics, and face mask wearing between continents and countries, we focussed on changes in Covid death rates in 2020. We have extended our Covid-19 multicompartment model (Khan et al., 2020) to fit cumulative case and death data for 49 European countries and 52 US states and territories during the recent pandemic, and found that the case mortality rate had decreased by at least 80% in most of the US and at least 90% in most of Europe. We found that death rate decreases do not have strong correlations to other model parameters (such as contact rate) or other standard state/national metrics such as population density, GDP, and median age. Almost all the decreases occurred between mid-April and mid-June 2020, which corresponds to the time when many state and national lockdowns were relaxed resulting in surges of new cases. We examine here several plausible causes for this drop-improvements in treatment, face mask wearing, new virus strains, testing, potentially changing demographics of infected patients, and changes in data collection and reporting-but none of their effects are as significant as the death rate changes suggest. In conclusion, this work shows that a two death rate model is effective in quantifying the reported drop in death rates.
受病毒株、年龄分布和口罩佩戴等方面在各大洲和国家可能存在差异的启发，我们专注于 2020 年新冠死亡率的变化。我们扩展了新冠多 compartment 模型（Khan 等人，2020 年），以拟合最近大流行期间 49 个欧洲国家和 52 个美国州和领地的累计病例和死亡数据，发现美国大部分地区的病死率至少降低了 80%，欧洲大部分地区的病死率至少降低了 90%。我们发现，死亡率的下降与其他模型参数（如接触率）或其他标准州/国家指标（如人口密度、GDP 和中位数年龄）没有很强的相关性。几乎所有的下降都发生在 2020 年 4 月中旬至 6 月中旬之间，这与许多州和国家放宽封锁导致新病例激增的时间相对应。我们在这里研究了这种下降的几个可能原因——治疗方法的改进、口罩的佩戴、新的病毒株、检测、受感染患者人群结构的潜在变化以及数据收集和报告方式的变化——但没有一个原因的影响能像死亡率的变化那样显著。总之，这项工作表明，双死亡率模型在量化报告的死亡率下降方面是有效的。
