Faculty of Public Health, University of Thessaly, Thessaly, Greece.
Department of Medicine and Surgery, University of Perugia, Perugia, Italy.
Sci Rep. 2021 Dec 10;11(1):23775. doi: 10.1038/s41598-021-02622-3.
Early warning tools are crucial for the timely application of intervention strategies and the mitigation of the adverse health, social and economic effects associated with outbreaks of epidemic potential such as COVID-19. This paper introduces, the Epidemic Volatility Index (EVI), a new, conceptually simple, early warning tool for oncoming epidemic waves. EVI is based on the volatility of newly reported cases per unit of time, ideally per day, and issues an early warning when the volatility change rate exceeds a threshold. Data on the daily confirmed cases of COVID-19 are used to demonstrate the use of EVI. Results from the COVID-19 epidemic in Italy and New York State are presented here, based on the number of confirmed cases of COVID-19, from January 22, 2020, until April 13, 2021. Live daily updated predictions for all world countries and each of the United States of America are publicly available online. For Italy, the overall sensitivity for EVI was 0.82 (95% Confidence Intervals: 0.75; 0.89) and the specificity was 0.91 (0.88; 0.94). For New York, the corresponding values were 0.55 (0.47; 0.64) and 0.88 (0.84; 0.91). Consecutive issuance of early warnings is a strong indicator of main epidemic waves in any country or state. EVI's application to data from the current COVID-19 pandemic revealed a consistent and stable performance in terms of detecting new waves. The application of EVI to other epidemics and syndromic surveillance tasks in combination with existing early warning systems will enhance our ability to act swiftly and thereby enhance containment of outbreaks.
预警工具对于及时应用干预策略以及减轻与具有流行潜力的疫情（如 COVID-19）相关的不良健康、社会和经济影响至关重要。本文介绍了一种新的、概念简单的预警工具——流行度波动率指数（EVI），用于预测即将到来的疫情浪潮。EVI 基于单位时间（理想情况下为每天）新报告病例的波动率变化，并在波动率变化率超过阈值时发出预警。本文使用 COVID-19 的每日确诊病例数据来演示 EVI 的使用。展示了基于 2020 年 1 月 22 日至 2021 年 4 月 13 日期间 COVID-19 确诊病例数的意大利和纽约州的 COVID-19 疫情结果。所有国家和美国各州的实时每日更新预测均可在线获取。对于意大利，EVI 的总体敏感性为 0.82（95%置信区间：0.75；0.89），特异性为 0.91（0.88；0.94）。对于纽约，相应的值分别为 0.55（0.47；0.64）和 0.88（0.84；0.91）。连续发布预警是任何国家或州主要疫情浪潮的强烈指标。EVI 在当前 COVID-19 大流行数据中的应用显示出在检测新疫情方面具有一致且稳定的性能。将 EVI 应用于其他疫情和症状监测任务，并与现有预警系统结合使用，将提高我们迅速采取行动的能力，从而加强疫情的控制。
