Directorate General for Health, Lombardy Region, Milano, Italy.
Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
Epidemics. 2021 Dec;37:100528. doi: 10.1016/j.epidem.2021.100528. Epub 2021 Nov 20.
In the night of February 20, 2020, the first epidemic of the novel coronavirus disease (COVID-19) outside Asia was uncovered by the identification of its first patient in Lombardy region, Italy. In the following weeks, Lombardy experienced a sudden increase in the number of ascertained infections and strict measures were imposed to contain the epidemic spread.
We analyzed official records of cases occurred in Lombardy to characterize the epidemiology of SARS-CoV-2 during the early phase of the outbreak. A line list of laboratory-confirmed cases was set up and later retrospectively consolidated, using standardized interviews to ascertained cases and their close contacts. We provide estimates of the serial interval, of the basic reproduction number, and of the temporal variation of the net reproduction number of SARS-CoV-2.
Epidemiological investigations detected over 500 cases (median age: 69, IQR: 57-78) before the first COVID-19 diagnosed patient (February 20, 2020), and suggested that SARS-CoV-2 was already circulating in at least 222 out of 1506 (14.7%) municipalities with sustained transmission across all the Lombardy provinces. We estimated the mean serial interval to be 6.6 days (95% CrI, 0.7-19). Our estimates of the basic reproduction number range from 2.6 in Pavia (95% CI, 2.1-3.2) to 3.3 in Milan (95% CI, 2.9-3.8). A decreasing trend in the net reproduction number was observed following the detection of the first case.
At the time of first case notification, COVID-19 was already widespread in the entire Lombardy region. This may explain the large number of critical cases experienced by this region in a very short timeframe. The slight decrease of the reproduction number observed in the early days after February 20, 2020 might be due to increased population awareness and early interventions implemented before the regional lockdown imposed on March 8, 2020.
2020 年 2 月 20 日夜晚，意大利伦巴第大区发现首例新型冠状病毒病（COVID-19）病例，这是亚洲以外地区的首例疫情。在接下来的几周内，伦巴第地区确诊感染病例数突然增加，因此实施了严格的措施来控制疫情传播。
我们分析了伦巴第地区发生的病例的官方记录，以描述 COVID-19 暴发初期的 SARS-CoV-2 流行病学。建立了实验室确诊病例的病例列表，并使用标准化访谈对病例及其密切接触者进行了回顾性整合。我们提供了 SARS-CoV-2 的序列间隔、基本繁殖数和有效繁殖数的时间变化的估计值。
流行病学调查在首例 COVID-19 确诊患者（2020 年 2 月 20 日）之前发现了超过 500 例病例（中位数年龄：69 岁，IQR：57-78 岁），表明 SARS-CoV-2 已经在伦巴第地区的 1506 个市镇中的至少 222 个（14.7%）市镇中传播，并且在整个伦巴第省都存在持续传播。我们估计平均序列间隔为 6.6 天（95%CI，0.7-19）。我们对基本繁殖数的估计范围从帕维亚的 2.6（95%CI，2.1-3.2）到米兰的 3.3（95%CI，2.9-3.8）。自首例病例确诊以来，观察到有效繁殖数呈下降趋势。
在首例病例通报时，COVID-19 已经在整个伦巴第地区广泛传播。这可能解释了该地区在很短的时间内出现大量重症病例的原因。在 2020 年 2 月 20 日之后的早期阶段，观察到繁殖数略有下降，这可能是由于公众意识的提高和 2020 年 3 月 8 日实施地区封锁之前采取的早期干预措施。
