• As the country comes out of lockdown, there will likely be a resurgence of SARS-CoV-2 infections.
• So, some level of physical distancing will be needed well into the future.
• Because of the risk that infections will spike again, intermittent physical distancing may be needed.

A modeling study of the new coronavirus, SARS-CoV-2, suggests that some amount of physical or social distancing will be needed in the United States well into 2022 to keep surges in COVID-19 cases from overwhelming the healthcare system.

The research, published April 14 in the journal Science, looked at a number of ways in which the virus might spread through the population over the next 5 years, including factors that can affect this spread.

Physical distancing has been a key approach in containing the current epidemic, as testing for the virus in many countries has been limited.

Also, there’s currently no effective treatment for COVID-19. A vaccine against the virus won’t be ready for at least 12 to 18 months.

Researchers from Harvard University’s T.H. Chan School of Public Health wrote that in the absence of a vaccine or treatment, it’s unlikely that physical distancing measures can be completely relaxed anytime soon.

However, they acknowledge that continued physical distancing — even if it’s done only every few months — will “present a substantial social and economic burden.”

They also emphasize that they’re not advocating for one particular course of action.

“We do not take a position on the advisability of these scenarios given the economic burden that sustained distancing may impose,” they write, “but we note the potentially catastrophic burden on the healthcare system that is predicted if distancing is poorly effective and/or not sustained for long enough.”

Modeling the post-pandemic virus spread

Caroline Colijn, PhD, a professor of mathematics and epidemiology at Simon Fraser University in Burnaby, British Columbia, says the researchers focused on some of the most important factors that can affect transmission of the virus over the next 5 years.

This includes whether there will be seasonal transmission of the virus, similar to the flu. Or whether people with an infection develop immunity, and how long it lasts.

Researchers also took into account whether exposure to other coronaviruses — such as those that cause the common cold — might provide people with some protection against SARS-CoV-2.

Many of these are unknowns.

For example, scientists don’t know yet know how much immune protection people develop after fighting off infection.

Immunity to coronaviruses that cause the common cold appears to last only about a year. Infection with the virus that causes SARS, though, results in longer lasting protection.

The researchers write that if immunity to SARS-CoV-2 isn’t permanent, the virus will likely enter into regular circulation in the population. Short-term immunity would favor yearly outbreaks, while longer-term immunity would favor outbreaks every 2 years.

If coronavirus transmission peaks in the winter, it would also coincide with the flu season, which could further strain healthcare systems.

Intermittent physical distancing needed

Physical distancing measures are effective at reducing the peak of the COVID-19 epidemic — or “flattening the curve.”

But they don’t eliminate the virus.

“This virus is not going anywhere. There is a distinct risk that we will see a sharp increase in the number of infections as we relax these social distancing measures,” said Dr. John B. Lynch, an associate professor of allergy and infectious diseases at the University of Washington, in a media briefing of the Infectious Diseases Society of America (IDSA) on Friday.

Colijn says there’s also a risk that if our current physical distancing measures work really well, they will leave the population with lower immunity against the virus.

“Then if we relax everything in the fall, and if seasonal effects amplify the transmission of the virus, we could be facing an even bigger peak in the fall,” she said.

This resurgence could be large enough that hospitals are once again overwhelmed.

Because of the risk that infections will spike again, intermittent physical distancing may be needed. In this approach, physical distancing measures are eased when possible, and then reapplied when infections start to rise again.

Singapore and Hong Kong are both pursuing this kind of “lift and suppress” strategy. But this approach depends on having widespread testing available.

“If we do get this epidemic under control with our distancing measures and we want to start relaxing them, we are going to need very high-quality monitoring. And that’s something that is going to have to involve testing,” Colijn said.

In this scenario, if the number of infections rises over a certain point, public health officials can reimpose physical distancing measures. When infections drop to a certain level, they can relax the measures again.

If the number of infections drops low enough, contact tracing and quarantining can be used to contain the spread of the virus.

Without testing, public health officials would need to rely on the number of COVID-19 patients in the ICU as an indicator of the resurging epidemic. But the Harvard authors point out there’s a large time lag between people getting sick and ending up in the hospital.

During this time, they can spread the virus to other people.

No one plan for how to end physical distancing

The United States is already looking forward to easing physical distancing measures.

On Thursday, President Donald Trump released guidelines meant to help states loosen their own restrictions, but leaving it up to states to decide on their own path forward.

The IDSA issued recommendations for what needs to be in place before reopening the country.

Right now, though, there’s no “best plan” for how to ease physical distancing measures. There will be a lot of trial and error moving forward.

The researchers point out that certain things could make it easier to lift physical distancing measures more quickly, such as a vaccine or treatment for COVID-19.

Aggressive contact tracing and isolation of people with an infection can also enable us to relax the physical distancing measures, they write. But again, this would require increased testing.

Lynch says that each city and state will do things differently because of differences in their healthcare capacity and public health infrastructure.

“We can start backing off social distancing, but we have to have the healthcare capacity to handle a possible surge in cases,” Lynch said. “We also need to have the public health infrastructure in place around contact tracing.”

But he agrees that we’ll be doing some level of physical distancing quite a ways into the future, with some people coming out of lockdown before others.

“As we back off on social distancing, it will be in a phased approach,” he said, “where certain parts of society relax a little bit, and others continuing with the more strict measures.”

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