Estimating unobserved SARS-CoV-2 infections in the United States
Estimating unobserved SARS-CoV-2 infections in the United States
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DOI：
10.1073/pnas.2005476117
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发表时间：
2020-09-08
影响因子：
11.1
通讯作者：
Poterek, Marya
中科院分区：
文献类型：
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作者：
Perkins, T. Alex;Cavany, Sean M.;Poterek, Marya
截至2020年3月，COVID-19导致全球数千人死亡并扰乱经济活动。由于病例定义狭窄和检测能力有限，在最初入侵美国期间未观察到的严重急性呼吸道综合征冠状病毒2（SARS-CoV-2）感染人数仍然未知。我们开发了一种方法，用于根据新传染病出现后不久通常可获得的数据估计未观察到的感染数量。从本质上讲，我们的做法的逻辑是，在输入性病例开始出现后的最初几周内，新感染病例的指数增长量是有限度的。将这一逻辑应用于截至3月12日的美国输入性病例和当地死亡数据，我们估计截至该日期美国发生了108，689例（95%后验预测区间[95%PPI]：1，023至14，182，310）感染。通过将模型对症状性感染的预测与当地报告的病例进行比较，我们获得了监测发现的症状性感染比例的每日估计值。这表明，整个2月，由于感染的指数增长超过了检测的增长，有症状感染的检测有所下降。在2月24日至3月12日期间，我们估计有症状感染的检测增加，这与检测增加密切相关（中位数：0.98; 95% PPI：0.66至0.98）。这些结果表明，在评估SARS-CoV-2最初入侵美国期间的传播程度时，检测是一个主要的限制因素。
By March 2020, COVID-19 led to thousands of deaths and disrupted economic activity worldwide. As a result of narrow case definitions and limited capacity for testing, the number of unobserved severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections during its initial invasion of the United States remains unknown. We developed an approach for estimating the number of unobserved infections based on data that are commonly available shortly after the emergence of a new infectious disease. The logic of our approach is, in essence, that there are bounds on the amount of exponential growth of new infections that can occur during the first few weeks after imported cases start appearing. Applying that logic to data on imported cases and local deaths in the United States through 12 March, we estimated that 108,689 (95% posterior predictive interval [95% PPI]: 1,023 to 14,182,310) infections occurred in the United States by this date. By comparing the model's predictions of symptomatic infections with local cases reported over time, we obtained daily estimates of the proportion of symptomatic infections detected by surveillance. This revealed that detection of symptomatic infections decreased throughout February as exponential growth of infections outpaced increases in testing. Between 24 February and 12 March, we estimated an increase in detection of symptomatic infections, which was strongly correlated (median: 0.98; 95% PPI: 0.66 to 0.98) with increases in testing. These results suggest that testing was a major limiting factor in assessing the extent of SARS-CoV-2 transmission during its initial invasion of the United States.