As the gears of the modern world grind to a near halt, one question is likely on the mind of many: When will the coronavirus pandemic — and social distancing — end?

No one knows for sure, but it’s probably not any time soon. Here’s what we do know about when it may be safe to come out of our homes and resume normal life.

The reason we may be in for an extended period of disruption is that the main thing that seems to be working right now to fight this pandemic is severe social distancing policies, says Adam Kucharski, an epidemiologist at the London School of Hygiene & Tropical Medicine and author of “The Rules of Contagion,” a book on how outbreaks spread.

Drop those measures — allow people to congregate in big groups again — while the virus is still out there, and it can start new outbreaks that gravely threaten public health.

We Need a Vaccine

The way things are looking now, we’ll need something to stop the virus to truly end the threat. That’s either a vaccine (there are some now entering clinical trials but it could be a year before they are approved) or herd immunity. This is when enough people have contracted the virus, and have become immune to it, to slow its spread.

Herd immunity is not guaranteed. Currently, it’s unclear if, after a period of months or years, a person can lose their immunity and become reinfected with the virus (which would make achieving herd immunity more difficult). Also, herd immunity will come at the cost of millions of people becoming infected, and possibly millions of people dying.

A sobering new report from the COVID-19 Response Team at the Imperial College of London underscores the need to keep social distancing measures in place for a long period.

Mitigation & Suppression

It outlines two scenarios for combating the spread of the outbreak. One is mitigation, which focuses on “slowing but not necessarily stopping epidemic spread.” Another is suppression, “which aims to reverse epidemic growth.”

In their analysis, isolation of confirmed cases and quarantine of older adults without social distancing would still result in hundreds of thousands of deaths, and an “eight-fold higher peak demand on critical care beds over and above the available surge capacity in both [Great Britain] and the US.”

Suppression, which requires “social distancing of the entire population,” can save more lives and prevent hospitals from becoming extremely overburdened. But it needs to be maintained “until a vaccine becomes available (potentially 18 months or more),” the report states. And it warns “transmission will quickly rebound if interventions are relaxed.” Make no mistake: Suppression comes at a huge cost to our society, economy, and perhaps even personal well-being.

What Kucharski and the new paper are arguing is that if you lift social distancing and don’t have a strong containment strategy in place to replace it, the virus is just going to cause new outbreaks. This virus is very contagious, with one person infecting 2 to 2.5 others on average without preventive measures. It’s also new, so no one is immune to it. This virus can spread before people show symptoms. That’s always going to make it hard to control and detect.

Social Distancing and Aggressive Testing

Caitlin Rivers, an epidemiologist at the Johns Hopkins Center for Health Security supports a program of general social distancing coupled with extensive testing, isolating new cases and tracing the people those who catch the virus have been in contact with. It’s the practices used in South Korea and Taiwan.

South Korea, for instance, reported its highest number of new cases, 909 on February 29. Since then, the number has steadily decreased. On March 24, only 76 new cases were reported.

The feasibility of such a program depends on many unknown variables. Firstly, it would require vastly more testing than is currently available. It also requires rigorous and rapid contact tracing after a positive case, which is.

Testing allows public health officials to identify new cases and isolate them, while tracing and testing their contacts as quickly as possible. Testing and isolating potential contacts before they develop symptoms is crucial, since the pandemic seems to be driven by people who don’t know they’re sick.

It would be “as though we’re back at the beginning of the outbreak and taking targeted approaches,” says Michael Mina, an epidemiologist at Harvard University’s T.H. Chan School of Public Health in Boston. With some luck, such an approach could keep outbreaks from spreading until a vaccine creates herd immunity.

However, until the United States ramps up its testing as widely as many other countries, the only tool the United States has to slow the virus’ spread is blunt, widespread social distancing.

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