The rule also gives the CDC ultimate authority to carry out medical tests and treatments, stating that “the individual's consent shall not be considered as a prerequisite to the exercise of any authority.” That’s medically unethical, says Hodge, since informed consent has been a bedrock of medicine for decades. “If you don’t get it, you could have additional quarantine, but you don’t get to force informed consent on people.”

Perhaps the most striking thing about these criticisms is how easy it would be for the CDC to have its cake and eat it. “There are really basic due process steps that could be put in place that would not undermine the CDC’s powers, but that would put in checks and balances so that when the powers are exercised, it’s done in a way that respects civil liberties,” says Alexandra Phelan from Georgetown Law School.

The stickier problem is that there’s little evidence to support screening or quarantining travelers. Consider the Ebola outbreak. The CDC screened more than 38,000 travelers flying into the U.S., by interviewing them and checking their medical records. They then monitored over 10,000 people for 21 days. And they caught exactly zero cases of Ebola.

You might ask: So what? Why take the chance? Why not ensure that we’ll catch the rare exceptions in the future? Here’s the thing, and it bears emphasizing: What you think would work in an outbreak often does not work. In these situations, so-called “common sense” can completely backfire.

“With Ebola,” says Nuzzo, screening doesn’t work because “you’re not transmissible until you’re really sick, and then you’re not moving.” It’s telling that Thomas Duncan, a Liberian man who was diagnosed with Ebola while visiting family in Dallas, didn’t spread the virus to anyone in his family or his community. He only transmitted it to two nurses who were caring for him long after it was obvious that he had Ebola.

Quarantines could also have serious unintended consequences. “You create the expectation that you can keep cases out by monitoring them, and there’s no evidence that we can do this,” says Nuzzo. If the disease does enter the country, that would seriously damage the credibility of health workers—the CDC included. When doctor Craig Spencer fell sick with Ebola in New York, after having helped with the outbreak in Guinea, he was vilified. People went on a witch hunt to find all the places he’d been to or eaten at, even though there was no risk of him spreading the virus at any of those places. “If we start monitoring people, it enforces that message.”

The distrust and confusion will be exacerbated if people fear that they will be quarantined unfairly; cases will go underground, and diseases will spread. And if health workers share those fears, they’ll be unwilling to travel to outbreak zones to help. That happened in the last Ebola outbreak: thanks to the CDC’s quarantines, the number of American health workers traveling to West Africa fell by 25 percent. Many worried that they would lose their jobs if they were isolated for weeks upon their return.