Reproductive number of the COVID-19 epidemic in Switzerland with a focus on the Cantons of Basel-Stadt and Basel-Landschaft
Reproductive number of the COVID-19 epidemic in Switzerland with a focus on the Cantons of Basel-Stadt and Basel-Landschaft
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DOI：
10.4414/smw.2020.20271
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发表时间：
2020-05-04
影响因子：
2.9
通讯作者：
Tanja, Stadler
中科院分区：
文献类型：
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作者：
Jeremie, Scire;Sarah, Nadeau;Tanja, Stadler
2020年1月30日，世界卫生组织（WHO）宣布2019冠状病毒病疫情为“国际关注的突发公共卫生事件”，中国各地的疫情从最初的几例迅速蔓延至数千例，并传入其他几个国家。2020年3月11日，世卫组织将疫情归类为大流行。瑞士、巴塞尔城市和巴塞尔乡村的首批病例分别于2020年2月25日、2月27日和2月28日确诊。截至2020年4月22日，瑞士共有28,154例确诊病例，其中巴塞尔城市州和巴塞尔乡村州分别有933例和811例。3月份确诊病例的迅速增加表明存在相当大的社区传播。我们估计了整个瑞士及其各州随时间推移的生殖数量，这些州有足够的数据。对于这一估计，我们使用了关于确诊病例和COVID相关死亡人数的公开数据，以及直接从巴塞尔大学医院和巴塞尔-Landschaft州公共卫生、经济和卫生局获得的额外数据。如果生殖数低于1，则该特定地点的疫情总体上得到控制，每天新增感染人数随着时间的推移而减少。如果这个数字大于1，那么疫情规模呈指数级增长。我们发现，瑞士的生殖数在3月的前三分之一期间在1.5到2之间，并一直下降到1左右。在2020年3月20日宣布最新的严格措施后，即禁止在公共场所聚集超过五人，生育人数大幅下降至1。我们估计，在4月的前三分之一，生殖数量在0.6到0.8之间。我们的敏感性分析解决了这样一个问题，即随着时间的推移，生殖数量的减少仅仅是检测强度降低的一个假象。总之，我们的结果表明，从3月的最后一周开始，瑞士的生殖数量明显低于1，因此疫情正在下降。然而，我们的分析并不允许我们确定这种下降的原因。从现在开始，我们将在网页上提供每日的生殖数量估计。在这方面需要注意的是，生殖数量的估计比最后一次数据收集日期晚10天左右，因为确诊是在感染后10天左右。
The World Health Organization (WHO) declared the COVID-19 outbreak a "Public Health Emergency of International Concern" on 30 January 2020, after rapid spread from a few initial cases to thousands of cases across China and introductions into several other countries. On 11 March 2020, the WHO classified the outbreak as a pandemic. The first cases in Switzerland, Basel-Stadt, and Basel-Landschaft were confirmed on 25 February, 27 February and 28 February 2020. As of 22 April 2020, there are 28,154 confirmed cases in Switzerland, including 933 and 811 in the Cantons of Basel-Stadt and Basel-Landschaft, respectively. The rapid increase of confirmed cases in March suggests considerable community transmission.We estimated the reproductive number through time for the whole of Switzerland and its cantons for which sufficient data are available. For this estimation, we used publicly available data on the number of confirmed cases and COVID-related deaths through time, as well as additional data directly obtained from the University Hospital of Basel and the Cantonal Office of Public Health, Economics and Health Directorate of Basel-Landschaft. If the reproductive number is below 1, the epidemic is overall under control for that specific location, with the number of new infections per day decreasing through time. If this number is above 1, the epidemic is exponentially increasing in size.We found that the reproductive number in Switzerland was between 1.5 and 2 during the first third of March, and has consistently decreased to around 1. After the announcement of the latest strict measure on 20 March 2020, namely that gatherings of more than five people in public spaces are prohibited, the reproductive number dropped significantly below 1. We estimated the reproductive number to be between 0.6 and 0.8 in the first third of April. Our sensitivity analyses addressed the concern of a decreasing reproductive number being merely an artifact of less intense testing through time.In summary, our results suggest that from the last week of March onwards, the reproductive number was significantly below 1 in Switzerland and thus the epidemic was declining. However, our analyses do not allow us to identify a cause for this decline. From now on, we will provide daily estimates for the reproductive number on our webpage. Important to note in this respect is that estimates of the reproductive number lag about 10 days behind the last date of data collection since confirmation of the diagnosis occurs around 10 days after infection.