Why new post-entry screening in the US is unlikely to catch Ebola

The Centers for Disease Control and Prevention just announced another initiative to keep Americans safe from Ebola — and like many things Ebola-related, it's more politics than prevention.

Starting on October 27, incoming passengers from the Ebola hot zone (Liberia, Sierra Leone, or Guinea) will report their temperature daily to a local or state health department for three weeks, the incubation period for Ebola. If they've developed any Ebola-like symptoms, they'll be put in isolation and treated. But experts say there are a number of things that will get in the way of identifying any new Ebola patients on US soil.

Why post-entry screening is unlikely to catch Ebola

For starters, there are probably few coming in. This latest initiative comes after the CDC already implemented exit and entry screening for passengers heading to the US from the most-affected countries.

Consider that, even before that exit or entry screening was put in place, we had a single passenger arrive to the US who developed Ebola. Tens of thousands of passengers have come in from West Africa since the epidemic started in March, and only one had Ebola. As the number of flights to the Ebola-affected region dwindles because some airlines have stopped flying there, the chances of another one reaching the US are small.

(Map courtesy of FiveThirtyEight.)

What's more, the new initiative relies on people to self-report their symptoms, and people, as we know, lie. Meanwhile, at this point many of the people coming in and out of the region are health and aid workers who would be required by their organizations to self-screen anyway, so a state initiative would be redundant.

An additional wrinkle in the plan: it'll be up to the state and local governments to coordinate and enforce, which will probably lead to a patchwork approach, at least as the protocols are being worked out. The University of Michigan's historian of medicine and pandemic expert Dr. Howard Markel pointed out that public health in America is the domain of the states, and states are already strapped for cash. Unless they ask the CDC for help, they'll need to absorb the costs and responsibility of post-entry Ebola screening.

It should avoid a travel ban — which is a good thing

All this isn't to say that this new plan is entirely useless. At the very least, it should ease the minds of the worried. And that's important, Markel said: "There are things you do for the public, not necessarily for the public's health." In this case, post-entry follow-up will be seen as an extra layer of protection for Americans from Ebola.

Writing in the New Republic, Jonathan Cohn also noted that this measure somewhat addresses the concerns of those who have been calling for travel bans, without the fall out and damage to the effort to stop Ebola in West Africa.

"That may not be enough for the political leaders who want to refuse entry altogether for visitors from the affected countries. As this argument goes, only a total ban will keep ebola from coming to and spreading in the U.S. But public health researchers and officials have warned repeatedly that such a comprehensive ban would be unlikely to do much good and might actually cause harm, by slowing the flow of aid workers and supplies to West Africa-where, despite the progress here and in countries like Nigeria, the epidemic is still raging."

The bottom line

Through post-entry screening, health officials just might catch another passenger or two who develop Ebola early, avoiding the bad optics and fumbling that happened in Dallas, and potentially, more Ebola cases in America. With a deadly disease like Ebola, Markel says that's a good thing: "As a physician, I don't want another case coming in."

But the problem with this epidemic isn't the one or two cases that might pop up in America, however immediately frightening they seem. It's the 10,000 in West Africa.

Even though this latest effort "seems like a reasonable, graded approach," Harvard's infectious diseases specialist Dr. Martin Hirsch told Vox, "Obviously, the major effort and resources should be and are being directed to containment of Ebola in Guinea, Sierra Leone and Liberia."

This is a point CDC director Tom Frieden has repeatedly and rightly made throughout this epidemic: to protect Americas, we need to protect West Africans. "We can't get to zero risk in US," Frieden has said, "until we stop the Ebola epidemic at its source in Liberia, Sierra Leone and Guinea."

But of course this isn't a perfectly rational world, and even Ebola — perhaps especially Ebola — will demand good political maneuvering as much as good public medicine.

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