Fisman David N, Greer Amy L, Tuite Ashleigh R
Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
Department of Population Medicine, University of Guelph, Guelph, Ontario, Canada.
Infect Dis Model. 2020 Jul 4;5:405-408. doi: 10.1016/j.idm.2020.06.004. eCollection 2020.
The use of masks as a means of reducing transmission of COVID-19 outside healthcare settings has proved controversial. Masks are thought to have two modes of effect: they prevent infection with COVID-19 in wearers; and prevent transmission by individuals with subclinical infection. We used a simple next-generation matrix approach to estimate the conditions under which masks would reduce the reproduction number of COVID-19 under a threshold of 1. Our model takes into account the possibility of assortative mixing, where mask users interact preferentially with other mask users. We make 3 key observations: 1. Masks, even with suboptimal efficacy in both prevention of acquisition and transmission of infection, could substantially decrease the reproduction number for COVID-19 if widely used. 2. Widespread masking may be sufficient to suppress epidemics where R has been brought close to 1 via other measures (e.g., distancing). 3. "Assortment" within populations (the tendency for interactions between masked individuals to be more likely than interactions between masked and unmasked individuals) would rapidly erode the impact of masks. As such, mask uptake needs to be fairly universal to have an effect. This simple model suggests that widespread uptake of masking could be determinative in suppressing COVID-19 epidemics in regions with R(t) at or near 1.
在医疗环境之外，使用口罩作为减少新冠病毒传播的手段已引发争议。口罩被认为有两种作用方式：它们可防止佩戴者感染新冠病毒；并防止亚临床感染者传播病毒。我们采用一种简单的下一代矩阵方法来估计在何种条件下口罩能将新冠病毒的再生数降低至1以下。我们的模型考虑了分类混合的可能性，即口罩使用者优先与其他口罩使用者互动。我们得出3个关键观察结果：1. 口罩即便在预防感染和传播方面的效果欠佳，但如果广泛使用，仍可大幅降低新冠病毒的再生数。2. 在通过其他措施（如保持社交距离）已使R值接近1的情况下，广泛佩戴口罩可能足以抑制疫情。3. 人群中的“分类”（即戴口罩者之间的互动比戴口罩者与未戴口罩者之间的互动更有可能发生的趋势）会迅速削弱口罩的作用。因此，口罩的佩戴率需要相当普遍才能产生效果。这个简单的模型表明，在R(t)等于或接近1的地区，广泛佩戴口罩对于抑制新冠疫情可能具有决定性作用。
