A diagram from the CDC site shows the floor plan of the 11th floor of a building in Seoul, South Korea, that was the site of a coronavirus disease outbreak in 2020. The blue shading shows the seating locations of people who became infected.

Editor’s Note: Kent Sepkowitz is a CNN medical analyst and a physician and infection control expert at Memorial Sloan Kettering Cancer Center in New York. The views expressed in this commentary are his own. View more opinion at CNN.

CNN  — 

The most complicated issue in America right now is how, when and where to reopen the cities and towns that have been sheltered in place. Everyone wants resumption of the mobile life of social proximity we enjoyed a few months ago but balancing this against the competing need to assure both individual safety and – because this is a contagious disease – societal safety remains a substantial challenge.

Fortunately, a new study from South Korea has just been published in “early release” form (it is final and peer-reviewed, just early) in the CDC medical journal, Emerging Infectious Diseases.

Titled “Coronavirus Disease Outbreak in Call Center, South Korea,” it describes how South Korea dealt with an outbreak in a high-rise building in the busiest part of Seoul with an early, decisive intervention that included closing the entire building, extensive testing and quarantine of infected people and their contacts. The study was conducted by experts from the Korea Centers for Disease Control and Prevention, the Seoul Metropolitan Government and other local institutions.

Though a one-building solution, the authors’ approach to identification and control of Covid-19 can serve as a blueprint for local and national policymakers wrestling with how best to proceed.

The outbreak was first recognized on March 8, 2020, approximately two weeks after South Korea found itself in the throes of a substantial national epidemic that arose from exposures at the Shincheonji Church in the city of Daegu, about 150 miles south of Seoul. About half of South Korea’s current toll of 10,738 confirmed cases are related to the Shincheonji Church outbreak.

Informed by previous outbreaks of SARS and MERS, South Korean health officials had a mature process for containment already in place when the first call center case was identified. A response team immediately undertook review of the site of the infections – a 19-story mixed commercial-residential building.

On March 9, one day after the first cases were reported, the entire building was closed. Testing was performed almost immediately on 1,143 people (workers, residents and a few visitors) with rapid results available to those affected and the team working to control the situation.

The testing showed that 97 people (8.5% of those occupying the building) were infected. Most of the cases were women in their 30s and almost all (94 of the 97) worked on the 11th floor of the building, in the call center.

Curiously, unlike many outbreaks reported before and since, virtually all of those infected – 92% of cases – had active Covid-19 symptoms at the time of diagnosis.

Investigators then constructed a detailed map of who was and was not infected, demonstrating that the overwhelming majority of cases had worked on one side of the 11th floor in extremely close proximity. Overall, 43% of all workers on the 11th floor developed infection with an even higher proportion among those in the heavily affected wing.

Next, the South Korean team tested the families and housemates of the 97 people with infection. Of these, about 16% were positive for Covid-19. Very surprisingly, no cases were diagnosed in the 15 home contacts of cases with “pre-symptoms” (nothing at time of test but development soon thereafter) or no symptoms at any time. This also goes against the current thinking on transmission, which is that it occurs even before people show symptoms.

In their discussion, the South Korean investigators reflected on the effect their work could have for business-as-usual in Seoul. They point out that the cases were in a “high-density work environment” and that spread was largely limited to one section of one floor.

But they fail to give themselves credit for what they accomplished. Yes, the distance between chairs and the duration of exposure are critical determinants of transmission at a single point in time – but allowing undiagnosed persons to unwittingly go about their business increases the opportunity for more and more uninfected people to have close and sustained contact with them, possibly leading to a secondary case.

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    Had the investigators waited a week, the infection would likely have spread widely to family, then to friends, then to friends’ workplaces – just as we are seeing in the outbreaks in US meat processing plants with a comparably high-density work environment. The virus knows no walls: Once a business is infected, the entire community may quickly become infected, unless dramatic action – such as occurred in Seoul – is taken.

    The current notion of some American public officials of simply reopening our cities and towns – like a department store grand opening that goes from nothing to a complete full-service store overnight – surely is a pipe-dream. But this report from South Korea shows us how we actually can handle the uncertain business of resuming a normal-ish life.

    To do so will require decisiveness such as quickly closing an entire building if needed, widely available testing with rapid results, and citizens willing to be quarantined as needed for the public good.

    Only by adopting this blueprint in its entirety can the vision of returning to a vibrant free-swinging nation be achieved. Trying to sneak back by ignoring the problem – a pandemic that has killed more than 60,000 Americans in two months – or by hoping that maybe it will go away if we eat this or drink that or don’t spend so much time worrying – will not only fail miserably, it will move us immediately back to the terrifying first weeks of March, when the sky actually felt like it was falling.