Health Surveillance and Safety Department, Regional Health Agency in the Ile-de-France Region (Agence Régionale de Santé d'Île-de-France), 13 rue du Landy, 93200 Saint-Denis, France.
(2) Santé publique France, French National Public Health Agency, Regional Unit (Cire) Ile-de-France, 13 rue du Landy, 93200 Paris, France.
J Infect Public Health. 2021 Nov;14(11):1733-1738. doi: 10.1016/j.jiph.2021.10.001. Epub 2021 Oct 6.
The 2020 COVID-19 pandemic led to a strict lockdown in France from March 17 to May 11, 2020. After the lockdown, the French strategy to mitigate the impact of SARS-CoV-2 relied partly on investigations of all confirmed cases. Monitoring collective settings is particularly important since SARS-CoV-2 seems prone to superspreading events (SSEs).
Our study is based on data gathered in Paris from May 11 to December 31, 2020, by the Ile-de-France Regional Health Agency (RHA) to investigate cases occurring in collective and high-risk settings. Specific events in high-risk settings were systematically transmitted to the RHA, and screenings were organized by the facilities, while other settings were reported when three cases were identified within a short period. These settings were more difficult to identify through the surveillance system since no systematic screening was organized by the facility, leaving screenings to rely on the national contact-tracing programme. No official superspreading threshold has been set for SARS-CoV-2. We defined a SSE as an event involving ten cases.
We analysed 15,706 events associated with 38,670 cases, representing an average of 2.70 cases per event. Most clusters occurred in educational facilities, workplace environments, social care settings, and healthcare facilities. SSEs represented 3.4% but accounted for 28% of all cases reported. The highest number of SSEs occurred in college settings (12.6%), followed by hospitals and retirement homes. Educational facilities had the lowest number of SSEs, with around 1% in preschools and elementary schools.
We observed different SSE rates in each setting. Preschools and primary schools represented the majority of events but experiencing very few SSEs. Colleges were prone to SSEs and were associated with a high number of secondary cases. These findings provide some insights on contact tracing activities and SARS-CoV-2 transmission in different settings.
2020 年 COVID-19 大流行导致法国于 2020 年 3 月 17 日至 5 月 11 日实施严格封锁。封锁后，法国缓解 SARS-CoV-2 影响的策略部分依赖于对所有确诊病例的调查。监测集体环境尤其重要，因为 SARS-CoV-2 似乎容易发生超级传播事件（SSE）。
我们的研究基于 2020 年 5 月 11 日至 12 月 31 日期间法兰西岛大区卫生局（RHA）在巴黎收集的数据，以调查发生在集体和高风险环境中的病例。高风险环境中的特定事件会被系统地传输给 RHA，并由设施组织筛查，而其他环境则在短时间内发现三例病例时报告。由于设施没有组织系统筛查，因此这些环境通过监测系统更难识别，筛查依赖于国家接触者追踪计划。SARS-CoV-2 尚未设定官方超级传播阈值。我们将 SSE 定义为涉及 10 例病例的事件。
我们分析了与 38670 例病例相关的 15706 个事件，平均每个事件发生 2.70 例。大多数集群发生在教育设施、工作场所环境、社会关怀环境和医疗保健设施中。SSE 占 3.4%，但占报告病例的 28%。SSE 数量最多的是大学环境（12.6%），其次是医院和养老院。教育设施的 SSE 数量最少，幼儿园和小学约为 1%。
我们观察到每个环境中的 SSE 发生率不同。幼儿园和小学占多数事件，但发生 SSE 的情况非常少。学院容易发生 SSE，与大量二次病例有关。这些发现为不同环境中的接触者追踪活动和 SARS-CoV-2 传播提供了一些见解。
