Americans have been told to hunker down at home for several weeks in order to slow transmission of the novel coronavirus, but a truly effective shutdown would likely have to be significantly longer and more severe.

The best way to prevent the pandemic from overwhelming hospitals is social distancing that could drag on for a year or more, until doctors find a way to control it, researchers at Imperial College London said in a report published Monday. They estimated 81% of people in Great Britain and the U.S. would get the virus if no steps were taken to slow its spread. In the U.S., 2.2 million would die, with 510,000 deaths in Great Britain.

Everyone who lives with an infected person would need to be quarantined, or schools would need to be closed, the report said. Moderate measures, such as insulating only vulnerable people and isolating those in contact with patients, will lessen the damage, but won’t be enough to avert millions of deaths, according to the new models.

Governments have latched onto the idea of social distancing, banning all large-scale activities and warning citizens to stay at least 6 feet away from others for the foreseeable future. The Trump administration asked Monday that Americans not gather in groups of 10 or more and avoid bars and restaurants for the next 15 days.

“The world is facing the most serious public health crisis in generations,” Neil Ferguson, an epidemiologist at Imperial College London, said in an email. To prevent the health system from becoming overwhelmed, large-scale social distancing “will need to be in place for many months — perhaps until a vaccine becomes available.”

The costs of such an ambitious effort to isolate people are far from clear. Even short-term distancing may create economic and social fissures that could take years to repair, while exacerbating existing inequities. The effects of a longer disruption would be even more consequential.

“It’s clearly best to start those interventions early and leave them in place from a disease control perspective,” said Marc Lipsitch, an epidemiology professor at the Harvard T.H. Chan School of Public Health. “But what’s right from a disease control perspective has to be balanced against what’s right for keeping society functioning.”

Draconian isolation measures as a tool for fighting outbreaks have their roots in history. During the 1918 Spanish flu, St. Louis swiftly implemented rules intended to slow its spread, helping to limit casualties. Philadelphia meanwhile waited weeks to put tighter controls in place, and paid the price with an overwhelmed health care system and more deaths.

In the century that has elapsed, the global economy has become more tightly integrated, and people move around the world more freely than ever before. That interconnectedness makes the calculus around severe disease-mitigation efforts more delicate.

While keeping a lid on the virus is important, human contact is critical for a wide range of things, Lipsitch said, including social well-being and mental health. Exactly how to balance the needs will be a political and policy decision.

“It’s important for education and it’s important for commerce; it’s important for keeping the economy going and for keeping people fed,” he said. “We sort of know what to do, but the challenge is that it could take quite a long time of doing it.”

The researchers at Imperial College London, who have been advising the World Health Organization, say there could be brief respites from the most severe measures as the months drag on, provided the workload lightens enough that hospitals can withstand another surge of cases.

“When you let up on those interventions, then transmission resumes,” said Lipsitch, who wasn’t involved in ICL’s modeling. “The virus doesn’t know that people were social distancing last week. It just knows that it can get from one person to another.”

The researchers examined the effectiveness of two strategies to blunt the pandemic. The first, mitigation, aims to slow the spread enough to blunt the peak of the epidemic. The other is suppression, an aggressive and prolonged approach intended to reverse the epidemic’s growth, similar to steps taken in China.

“Mitigation is unlikely to be a viable option without overwhelming health care systems,” the researchers concluded in their report.

Steps including isolating patients, plus home quarantines for their family members and society-wide social distancing, could reduce deaths in Great Britain to around 100,000 over two years, the researchers estimated. The policies would continue for months, lifted only during periods when ICUs had room to handle a surge of patients.

If school closures were added, the deaths could be lowered to 40,000, they said.

“It will be necessary to layer multiple interventions,” the Imperial College researchers say in their report. “These policies will need to be maintained until large stocks of vaccine are available.”

It is expected to take a year to 18 months to develop a widely available coronavirus vaccine. The first immunization designed specifically for the virus that causes Covid-19 began testing on Monday.

There are trade offs that will need to be made, and the wrong approach could create more harm than good, said Savi Maharaj, head of the biological modeling research group at the University of Stirling in the U.K.

“Pretty much for all diseases, doing social distancing very severely and early on — such as closing things quickly and locking it down — can be the optimal approach,” she said. “The epidemic dies out very quickly.”

The cost, however, can be very high.

A simulation designed to look at what people would do in the real world found they did adopt some social distancing, but not enough to halt the outbreak. With milder measures, an epidemic will persist but the number of cases will be distributed over a longer period, allowing health systems to keep up.

“What our study showed is that even moderate social distancing has the benefit of flattening the curve and reducing the peak of disease at any one given time,” she said. “The downside of that is the epidemic lasts longer and the period of social distancing that’s needed is longer.”

That may be more realistic.

“In the real world, we aren’t able to achieve a complete lock down,” she said. “The societies we live in aren’t closed. Even if one country did a complete lock down, there is the question of whether they can prevent the virus from coming back.”


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