14-Day Quarantines Should Keep You Home

(Bloomberg Opinion) -- Just in time for the July 4 holiday, a whole new series of rules and regulations surrounding interstate travel have suddenly sprung up in the Northeastern United States. These may be motivated by the desire of governors and their constituents to minimize Covid-19 cases in their own states, but there's also a wider scientific rationale for the various 14-day quarantine requirements in place in New York, New Jersey, and the six New England states. In fact, the main benefit of the lengthy quarantine period may be convincing most people to stay home — or at least, very close to it.  

Keeping people in their home states can cut coronavirus spread everywhere, says Arnout van de Rijt, a sociologist and network theorist at the European University Institute.

A model he and colleagues created suggests that spreading the disease to distant people is much worse than spreading it to the same number of neighbors — sort of the way a cancer gets much worse every time it metastasizes. 

“This is the networked nature of things,” he says. “If Texas cannot generate a second wave in New York, then New York cannot re-infect Florida in the future, and so on. By protecting New York, Cuomo is protecting America as a whole.” While the rationale of 14-day quarantines may be to protect individual states, the benefit is more universal. 

It's all bad for the travel industry, of course. A few weeks ago, many of these same Northeastern states were the epicenter of the disease. Now they are seeing declining rates of positive tests, hospitalizations and deaths — a situation that feels hard-earned and tenuous to those of us who live here. That's why until very some recent rule changes, even many New Englanders weren't able visit our neighboring states without jumping through hoops that made an out-of-state vacation untenable.

Maine and New Hampshire won't let in most visitors without either securing a negative test within 72 hours of arrival or quarantining for what's become a standard period of 14 days. Vermont, Rhode Island, and Massachusetts have their own patchwork of rules, while Connecticut has thrown in with its Mid-Atlantic neighbors imposing a 14-day quarantine for certain out-of-state visitors. 

The 14-day quarantine period is based on what scientists estimate to be the maximum disease incubation time — the time between when an infected person is first exposed and when symptoms appear. The average is five days, but there's a lot of variation. By 14 days, according to the latest estimates, 99% of people who are going to get symptoms will feel them. Experts say by this time, most asymptomatic cases will have run their course and passed their infectious window, though these cases are still not well understood. 

The model van de Rijt helped create projects what might happen after lockdown measures are eased. With no continuing restrictions or voluntary changes, the disease would simply rebound and start growing exponentially again. Such a rebound — like the one we're seeing now in the South and West — is to be expected because there's no natural mechanism by which the disease would stay in check once human behavior reverts to normal.

The virus won't really be under control until there's a vaccine, but that doesn't mean we need to go back into full lockdown. Measures much less drastic than shutting down the economy should be able to clamp down on the spread enough to prevent big infection spikes and hospitals becoming overwhelmed. Those measures can include encouraging people to social distance, wear masks and avoid crowds — and encouraging people to stay in their own communities and avoid long-distance travel. 

If people stay local, the disease spreads more slowly, like a storm front, van de Rijt says. But long-distance connections are disease accelerators. The seeds of new outbreaks get planted.

Of course, if people do stay isolated for 14 days, they are very unlikely to allow any of those seeds to plant, which raises the question of whether that time period is excessive. The statistics on incubation say you'd catch at least 97% of infections with just an 11-day quarantine. 

Would a shorter quarantine period encourage more compliance? Are we making the perfect the enemy of the good? Maybe — but if there's one thing that's even harder to predict than the behavior of a new virus, it's the way people will behave in the face of that new virus. 

For now, we'll just have to try to make the most of being stuck close to home. At least it's better to be confined to your state than confined your house.

The tests seem like the easy option, but results can take a day or two, and many states still only allow them for people who are sick or essential workers.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.

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