Opponents of immigration almost instantly latched onto Ebola (see here, here and here for starters).  Isn’t this horrific disease the “killer argument” showing that open borders is a naively deadly proposal?  The Center for Immigration StudiesMark Krikorian swiftly coined the Twitter hashtag #LibertariansForEbola to drive the argument home.

Some libertarians downplay the risk of Ebola, even comparing it to statistically microscopic dangers like terrorism.  While I agree that Americans now overestimate their risk of Ebola infection, this plague nevertheless deserves our full attention.  Throughout history, contagious disease has killed billions.  Even today, contagious disease causes 16% of all global deaths.  Contagious disease is at least a thousand times as deadly as terrorism.  And as I have said many times, the moral presumption in favor of open borders is only that – a presumption.  If open borders in the face of Ebola had awful overall consequences, and there were no cheaper and more humane remedy than immigration restrictions, some restrictions would be morally justified and I would support them.  The key question, then, is: Would open borders in the face of Ebola have awful consequences?
From a long-term perspective, the effect of open borders on Ebola is anything but awful.  Open borders is the greatest remedy for poverty ever discovered.  Ebola is a classic disease of poverty – highly contagious in a poor society, but only slightly contagious in a rich society.  In poor societies, untrained laymen unsanitarily care for the severely ill, dispose of the dead, and prepare meat.  In rich societies, specialized experts perform all these tasks.  And as the World Health Organization explains, unsanitary treatment of the living, the dead, and meat account for almost all Ebola contagion.  If you want to eliminate serious contagious diseases like Ebola during the next few decades, open borders is probably the best way to do it.
From a short-term perspective, however, the effects of open borders on Ebola are admittedly less clear.  Risks are miniscule under current U.S. conditions.  The only at-risk population inside the U.S. seems to be health workers who care for Ebola patients.  Even the Texas family who lived with Liberian Ebola victim Thomas Duncan look fine; they’re nearly out of quarantine.  
Under full open borders, however, West Africans could enter the U.S. as easily as Virginians enter Maryland.  There is every reason to think that hundreds of thousands of people from Liberia, Guinea, and Sierra Leone would jump at the opportunity.  And while most would be healthy, a sizable minority would be infected – possibly so many that existing U.S. health facilities would be unable to safely isolate them.  Health workers’ risk of catching Ebola from their patients amplifies this scarcity – for every doctor or nurse who catches Ebola, how many others will refuse to expose themselves to the disease?
Fortunately, only mild departures from full open borders are necessary to avert this scary scenario.  The obvious keyhole solution: Instead of freely admitting everyone from affected countries, freely admit everyone from affected countries who provides a clean bill of health and accepts a standard 21-day quarantine.  
On balance, then, horrible contagious diseases like Ebola make open borders look better, not worse.   In the short-run, token restrictions are enough to prevent spreading Ebola from the Third World to the First.  And in the long-run, open borders is the quickest, surest way to make diseases of poverty history.
Parting thought for all you citizenists out there: As long as the Third World remains poor, it will remain fertile breeding ground for horrible contagious diseases.  Some of these diseases are likely to be far more contagious than Ebola – too contagious for the most draconian border controls to keep out.  A re-run of the 1918 flu would kill two million Americans.  Eradicating poverty in the Third World is therefore clearly in the interests of your countrymen, present and future.  If you’ve got a quicker cure for Third World poverty than open borders, I’d like to hear it.