[论文解读] The early phase of the COVID-19 outbreak in Lombardy, Italy

Danilo Cereda, Marcello Tirani+22 more|arXiv (Cornell University)|Mar 20, 2020

COVID-19 epidemiological studies参考文献 2被引用 276

一句话总结

研究伦巴第地区前5,830例实验室确诊病例，估算基本再现数和世代间隔，并突出早期广泛传播和医疗系统负担。

ABSTRACT

In the night of February 20, 2020, the first case of novel coronavirus disease (COVID-19) was confirmed in the Lombardy Region, Italy. In the week that followed, Lombardy experienced a very rapid increase in the number of cases. We analyzed the first 5,830 laboratory-confirmed cases to provide the first epidemiological characterization of a COVID-19 outbreak in a Western Country. Epidemiological data were collected through standardized interviews of confirmed cases and their close contacts. We collected demographic backgrounds, dates of symptom onset, clinical features, respiratory tract specimen results, hospitalization, contact tracing. We provide estimates of the reproduction number and serial interval. The epidemic in Italy started much earlier than February 20, 2020. At the time of detection of the first COVID-19 case, the epidemic had already spread in most municipalities of Southern-Lombardy. The median age for of cases is 69 years (range, 1 month to 101 years). 47% of positive subjects were hospitalized. Among these, 18% required intensive care. The mean serial interval is estimated to be 6.6 days (95% CI, 0.7 to 19). We estimate the basic reproduction number at 3.1 (95% CI, 2.9 to 3.2). We estimated a decreasing trend in the net reproduction number starting around February 20, 2020. We did not observe significantly different viral loads in nasal swabs between symptomatic and asymptomatic. The transmission potential of COVID-19 is very high and the number of critical cases may become largely unsustainable for the healthcare system in a very short-time horizon. We observed a slight decrease of the reproduction number, possibly connected with an increased population awareness and early effect of interventions. Aggressive containment strategies are required to control COVID-19 spread and catastrophic outcomes for the healthcare system.

研究动机与目标

• 描述意大利伦巴第地区COVID-19早期流行病学特征。
• 估算关键传播指标（基本再现数、世代间隔）。
• 评估初始疫情暴发期间的临床特征、住院情况和ICU需求。
• 确定干预措施的时机及其对传播动态的潜在影响。

提出的方法

• 对确诊病例及其密切接触者进行标准化访谈，收集人口统计信息、症状起始时间、临床特征、呼吸道样本、住院情况和密切接触者追踪数据。
• 从观测数据中估计基本再现数（R0）和世代间隔。
• 评估有症状与无症状个体之间病毒载量的差异。
• 时序分析以观察净再生数随时间的变化。

实验结果

研究问题

• RQ1 早期伦巴第疫情的估计基本再现数（R0）是多少？
• RQ2 在此次队列中SARS-CoV-2传播的平均世代间隔是多少？
• RQ3 实验室确诊病例中有多少比例需要住院及ICU治疗？
• RQ4 在2020年2月20日左右传播是否下降，以及这是否与意识提高或干预措施有关？
• RQ5 有症状与无症状个体之间的病毒载量存在差异吗？

主要发现

• R0 估计为 3.1 (95% CI, 2.9 到 3.2)。
• 平均世代间隔估计为 6.6 天 (95% CI, 0.7 到 19)。
• 病例中位年龄为 69 岁（范围 1 个月到 101 岁）。
• 47% 的阳性受试者住院，其中 18% 需要重症监护病房。
• 在检测到首例病例时，伦巴第南部大多数市镇的疫情已经开始，表明早期已经传播。
• 净再生数的下降趋势大约在 2020 年 2 月 20 日开始，可能与意识提升和早期干预有关。
• 有症状和无症状病例之间的病毒载量没有显著差异。
• 被认为需要积极的遏制策略来控制传播，避免对医疗系统造成灾难性负担。