Auranen Kari, Shubin Mikhail, Karhunen Markku, Sivelä Jonas, Leino Tuija, Nurhonen Markku
Department of Mathematics and Statistics, Department of Clinical Medicine, University of Turku, Turku, Finland.
Department of Public Health Solutions, Finnish Institute for Health and Welfare (THL), Helsinki, Finland.
Epidemiology. 2021 Jul 1;32(4):525-532. doi: 10.1097/EDE.0000000000001344.
Information about social mixing patterns under heavy social distancing is needed to model the impact of nonpharmaceutical interventions on SARS-CoV-2 transmission.
We conducted a survey on daily person-to-person contacts during the early phase of the SARS-CoV-2 epidemic in Finland, one month after strong social distancing measures had been introduced nationwide. We defined a contact as exchange of at least a few words in proximity of another person. We also considered physical ("skin-to-skin") contacts separately. Based on 3,171 reported contacts by 1,320 participants of 1-79 years of age, we estimated age-stratified contact matrices essential in modeling virus transmission.
Compared with contacts during prepandemic conditions, as learned from the Finnish part of the Polymod study, there was a 72% (95% credible interval, CI = 71, 74) reduction in the daily number of all contacts and a 69% (95% CI = 66, 73) reduction in the daily number of physical contacts in April 2020. The largest reduction, of almost 90%, occurred in physical contacts by individuals more than 70 years of age. The estimated reduction in the transmission potential of the virus attributable solely to reduced contact frequencies varied between 59% (whole population; physical contacts; 95% CI = 52, 68) and 77% (over 20-year olds; physical contacts; 95% CI = 70, 89).
We surmise that the large reduction in the daily numbers of social contacts in the early part of the SARS-CoV-2 epidemic in Finland was likely a major contributor to the steady decline of the epidemic in the country since early April.
为了模拟非药物干预对严重急性呼吸综合征冠状病毒2（SARS-CoV-2）传播的影响，需要了解严格社交距离下的社会混合模式信息。
在芬兰全国实施严格社交距离措施一个月后，即SARS-CoV-2疫情早期，我们开展了一项关于每日人际接触情况的调查。我们将一次接触定义为在他人附近至少交谈几句话。我们还分别考虑了身体（“肌肤接触”）接触。基于1320名年龄在1至79岁的参与者报告的3171次接触，我们估算了对病毒传播建模至关重要的按年龄分层的接触矩阵。
从多模式研究的芬兰部分了解到，与疫情前的接触情况相比，2020年4月所有接触的每日数量减少了72%（95%可信区间，CI = 71, 74），身体接触的每日数量减少了69%（95% CI = 66, 73）。70岁以上人群的身体接触减少幅度最大，近90%。仅因接触频率降低导致的病毒传播潜力估计降低幅度在59%（全体人群；身体接触；95% CI = 52, 68）至77%（20岁以上人群；身体接触；95% CI = 70, 89）之间。
我们推测，在芬兰SARS-CoV-2疫情早期，社交接触的每日数量大幅减少可能是该国自4月初以来疫情稳步下降的主要原因。
