Quarantine, as the researchers explain, comes from the Italian word quarante, a reference to the 40-day period incoming ships were sequestered during plague outbreaks in the 13th century. Although the modern word has gathered a variety of meanings, the scientists say it’s best understood as “compulsory physical separation” or segregation from the population of healthy people potentially exposed to a contagious agent.

Barbera’s group describes three times when quarantines have been applied in the United States in response to an infection threat with poor results. In one, a 1893 outbreak of smallpox in Muncie, Ind., the effort led to healthy people being sequestered with sick family members, roving patrols of armed enforcers, and arrests of quarantine scofflaws. The public became irate, and several public officials were shot, leading them to declare the move “an utter failure.”

And in a 1900 episode, San Francisco officials trying to prevent spread of plague in a Chinese neighborhood “arbitrarily” locked down only Chinese households and business, doing grave damage to the economy of the community.

That response was ultimately found unconstitutional. However, Barbera’s group argues, it illustrates the significant risk that quarantine efforts may unfairly penalize minorities and the politically disconnected.

Elizabeth Fenn, author of the book Pox Americana, a history of smallpox’s role in the early history of the United States, calls the 19th century’s record on quarantines “horrific” in terms of their application against minorities and immigrants. “If you were white and wealthy you weren’t quarantined, but if you were a Jewish immigrant from Eastern Europe you were,” says Fenn, who teaches early American history at George Washington University.

However, she adds, “I think it’s clear that quarantines are effective” at preventing the spread of infections, as long as they’re applied properly. Whether they violate civil rights, and whether they’re legal, are debatable. “At what point does the good of the whole override the rights of the individual? It’s [an issue] that needs to be decided,” she says.

O’Toole hopes politicians and public health officials will consider the new report as they try to refine their emergency plans. She and her colleagues also recommend more investment in emergency management technologies and better communication between scientists, politicians, and the public.

The conclusions aren’t limited to bioterrorism, but apply to naturally occurring emerging infections as well. “We’re all trying to rethink epidemics in the 21st century and we need to rethink them,” she says.