An aid worker tosses a small bag of water to quarantined West Point residents last week. (Abbas Dulleh/AP)

As the Ebola outbreak spread beyond its control, the Liberian government took the extraordinary step last week of quarantining the entire slum of West Point, an area near the capital of Monrovia, with barbed wire and wooden barricades. With 70,000 people trapped, rioting ensued. A teenager died after he was shot by troops enforcing the cordon.

A county in North Carolina is quarantining anyone who worked with or around Ebola-stricken West African patients in an RV park, regardless of whether they show symptoms of contracting the disease.

Such moves have obvious appeal to a public worried about an incurable disease that kills 60 percent of the people who contract it. But in fact they make matters worse. The quarantine in West Point is a recipe for disaster.

A vestige of the Middle Ages, the term “quarantine” originates with the Black Death, the calamitous outbreak of plague that decimated Europe in the 14th century. To ensure that plague was not introduced into a port, ships in the harbor were forced to wait 40 days before they were allowed to disembark passengers.

But a quarantine, or cordon sanitaire, restricts the movement of individuals who may be healthy and pose no risk to others, such as those in North Carolina's Mecklenburg county. Quarantining individuals who have no symptoms is not justified. It is not evidence-based.

Much worse, it may prohibit the critical basics of civilized society from entering the quarantined region, as is happening in West Point. There, the situation is much more dire, with water, food and medical supplies becoming scarce in the quarantine zone. Total breakdowns in law and order, barbarism and lethal force exerted against those who defy orders are serious concerns in quarantined regions.

Even worse, a disease like Ebola, free of the sterilizing effects of civilization, can flourish in such environments, where bodies, waste and refuse collect. This provides ample opportunity for the virus to prey on healthy people, potentially increasing the burden of infection. And those healthy people quarantined may turn against their government, which is violating the very liberty it is constituted to protect.

Where quarantine, or more accurately, "isolation" is effective is in the treatment of individuals with symptoms of contagious diseases, who must be separated from others to decrease the spread of infection. Quarantine periods are ended when it is apparent that the individuals are free from disease. Isolation can be applied to a contagious tuberculosis patient, for example, who represents a true risk of spreading the infection to others. In fact, authorities in California's Santa Barbara County issued an arrest warrant last week for a tuberculosis patient who discontinued his treatment and vanished.

While decisive action is needed to combat Ebola and other diseases, the quarantine of a geographic location applied to people without evidence of infection functions not to control disease but to promote its further development.

Amesh Adalja is an infectious diseases physician at the University of Pittsburgh Medical Center (UPMC) and a faculty member in the Division of Infectious Diseases at the University of Pittsburgh School of Medicine. He is on Twitter @AmeshAA and his blog