Recent Texas and New York City Ebola cases put the concept of quarantine back into the American lexicon. A period of mandatory isolation, of people and/or animals, quarantine is an extreme measure taken to prevent the spread of infectious diseases. Such forms of enforced isolation are referenced as far back as the Old Testament, while the word “quarantine” itself dates to the late medieval Plague.

When the Black Death reached Europe in the middle of the 14th century, ultimately killing a third of the population, extreme measures were taken to try to control the terrible disease.  Many of these were akin to magic and utterly useless. But in Venice-controlled Ragusa (now Dubrovnik, Croatia), one of these infection controls was the trentino, a period of thirty days of isolation, which was instituted in 1377.  It had some positive effect. Over the next 80 years, similar laws were introduced in other Mediterranean cities, with the period of isolation extending to forty days, or quarantino. In his short note on “The Origin of Quarantine,” Paul S. Sehdev gives several hypotheses for why 40 days was finally settled on, including Biblical parallels and ancient Greek medical doctrine. (The word is still used, but today the number of days of a quarantine may well vary from 40.)

The recent quarantines in Texas and New York are both local affairs. But the federal government can also impose quarantine, though it has rarely done so in the last half century. In the Columbia Law Review, Arjun K. Jaikumar looks at this history and the legal basis for such action.  He reasons that a recent Supreme Court decision may undermine federal power in this area. Quarantine now “may in fact be unconstitutional despite more than a century of Supreme Court acceptance of federal quarantine authority under the Commerce Clause.”

It’s a troubling thought, but Jaikumar finds some legal wiggle room for allowing the Commerce Clause’s purview to hold. It’s a  discombobulating notion that the Commerce Clause of the U.S. Constitution holds such sway over public health. Infectious diseases are, in this reading, a form of interstate commerce.

Quarantine is inevitably a conflict between individual civil liberties and public health. So how do we reconcile these sometimes opposing positions? A democracy shouldn’t be flying by the seat of its hospital scrubs in such matters.