来源 :中华考试网 2021-06-22中
“Social distancing” is, in fact, an umbrella term that comprises several very complex interventions for keeping healthy people spaced apart from anyone who could be infectious. Measures range from telling people to avoid crowds to issuing wholesale stay-at-home orders, with just about endless variations and possible combinations. Each of these may work to differing degrees, and they come with varying social and economic costs. When we ask whether social distancing “works,” we’re collapsing all these boundaries.
In general, once it’s clear the spread of a new virus as dangerous as this one has not been contained by testing and contact tracing, and for which there isn’t any treatment or vaccine, more drastic forms of social distancing are the only options left to slow it down. But the body of knowledge about social distancing in all its forms is changing rapidly in real time, as the pandemic brings a blizzard of new data, research, and analysis. Say anything on some subjects, and there’s quite a good chance it could be out of date in hours, if not minutes.
First, on the question of large gatherings, and the degree to which their prohibition slows viral spread. Covid-19 outbreaks appear to have spiraled out from large religious meetings both in South Korea and in France, each resulting in thousands of infections. A soccer match was at the epicenter of Italy’s devastating wave. Avoiding crowded living conditions, though, isn’t always feasible.
What about travel restrictions? A systematic review of research on their deployment to prevent the spread of influenza looked at 20 studies conducted through May 2014. The link between travel and contagion appeared to be significant: When there was more travel, for example around Thanksgiving, more people got influenza; in contrast, when air travel decreased after 9/11, the rate of influenza decreased. Taken together, the studies suggest that domestic travel restrictions can delay influenza outbreaks for about a week; while international border closures may extend that window to 2 months.
Data from the Covid-19 pandemic might change the balance of evidence here. Restricting travel from Wuhan around Chinese Lunar New Year was seen as a success in helping to stop the spread of the coronavirus across China. A modeling study based on Wuhan data concluded that if international travel restrictions were combined with contact tracing and quarantine, it might be possible to keep the disease under control. Several countries may try to last the distance to a vaccine this way. Australia and New Zealand, for example, may allow cross-border travel only within their shared bubble of well-controlled infection rates; and perhaps to other countries in the region, too, if they become and stay Covid-19-free.
The question of school closures has been especially contentious, given the major social costs of the intervention.