Between October 21 and 25, House and Senate candidates ran 734 ads citing the threat of Ebola. Some candidates charged that by failing to secure the border with Mexico, Democrats were allowing cases of Ebola into the United States. North Carolina Republican Thom Tillis, who is running for Senate, warned, "We've got an Ebola outbreak, we have bad actors that can come across the border; we need to seal the border and secure it.” Other candidates have linked border immigration to ISIS, suggesting that Islamist terrorists would be crossing the border to threaten Americans. The Republican National Committee ran an ad that concluded, “Vote to keep terrorists off U.S. soil.” Several candidates, including Kentucky Senator Mitch McConnell, included video from ISIS in their ads.

These ads may or may not sway voters, but they are responding to widespread fear of Ebola and ISIS. Voters regard the American response to these threats as being among the most important issues in this election. In an extensive AP poll taken in mid-October, 73 percent of likely voters ranked the threat ISIS and 74 percent the danger of Ebola as “extremely or very important.” A Harvard School of Public Health poll found that 39 percent of Americans believe that there will be a large-scale Ebola epidemic, and 26 percent believe that someone in their immediate family will get it.

Not all fears are irrational, but there is a sheer element of nuttiness in these current fears. There has been and is no epidemic in the United States. There have now been only four cases of Ebola in the United States, one of which resulted in a fatality. Several hundred people died last winter from the swine flu without causing a similar panic. ISIS is clearly an evil outfit, and there may be good foreign policy grounds for attempting to contain or defeat it. But it appears to have far less ability to directly threaten the United States than Al Qaeda and its various affiliates. Yet, according to an NBC poll, 47 percent of Americans think the United States is “less safe” than it was before September 11.

Why, then, have these irrational fears arisen? The easy answer is to blame the media for publicizing ISIS’s exploits or the spread of Ebola in Africa or to point the finger at politicians for exploiting these fears, but that seems to me to be too easy. Americans had these kind of irrational panics—notably about drugs in the late 1980s—well before the internet and the 24-hour-news cycle. And Republicans (and some Democrats who wanted to blame Republican funding cuts for the threat of Ebola) were exploiting or heightening fears that already existed. They magnified these fears, but they didn’t create them. I don’t have a final, and clear, explanation for these fears, but I want to offer some possible explanations for what appears to be a case of mass hysteria.

1. Mortality Cues

In the wake of September 11, and of the anthrax letters, Americans feared new terrorist attacks, and credited George W. Bush and the Republicans with warding them off. These fears lingered, however, well after there were reasonable grounds for expecting an attack, and were more prevalent in a state like West Virginia or Idaho than in a state like New York that might have been a more obvious target for a terrorist group. In trying to explain how these fears had affected the election of 2004, I discovered the work done by three psychologists, Sheldon Solomon, Jeff Greenberg, and Tom Pyszczynski, who, inspired by the late anthropologist Ernest Becker, developed a theory they called “terror management.” They devised ingenious experiments to show that the mere thought of one's mortality—delivered even through subliminal cues—can trigger a range of emotions, from disdain for other races, religions, and nations, to a preference for charismatic over pragmatic leaders, to a heightened attraction to traditional mores.

What distinguished Americans’ reaction to ISIS from its reaction to Bashar Al Assad (who has brutally murdered many thousands of Syrians) or to the Al Nusra Front, which professes a similar ideology to ISIS, and also controls territory in Syria, is that through its  video of an American journalist being beheaded, ISIS triggered mortality cues. As a result, Americans who opposed retaliating against Assad for his use of chemical weapons, and favored total withdrawal from Iraq, have overwhelmingly favored—by 70 percent, according to one poll—sending American advisors, planes, and missiles to aid in the fight against ISIS. Some foreign policy officials may favor intervention for humanitarian or geopolitical reasons, but those kind of considerations are not behind the widespread public support for intervention. That’s driven by fear that has been cued by the beheading videos.

2. Race and the Plague

Would Americans have panicked about Ebola if there were reports of a deadly flu that had spread from Canada to the United States? Earlier this year, stories about the outbreak of the avian flu in China failed to prompt calls for a ban on flights from China. I suspect that the panic over Ebola has something to do with its origins in Africa and its association with blackness and black people. As Winthrop Jordan wrote in his pathbreaking book, White over Black, the English, and many of the English settlers to North America, associated blacks with “baseness and evil.” Blackness was “a sign of danger and repulsion.” That association has endured and contributes to the American fear of contagion from Africa.

Four psychologists from the University of British Columbia, Jason Faulkner, Justin Park, Mark Schaller, and Lesley A. Duncan, conducted studies over a decade ago of whether xenophobic attitudes contribute to the fear of disease from certain regions. One of their studies found that people who thought of themselves as vulnerable to disease had far more negative reactions toward immigrants from East Africa than from Eastern Asia or Eastern Europe. (Ebola, of course, originates in West rather than East Africa, but that doesn’t change the thrust of these findings about attitudes toward disease in Africa.) Political scientists Laura Seay and Kim Yi Donne draw a similar connection between Americans’ irrational fear of an Ebola outbreak and the disease’s origins in black Africa.

3. Nativism and the Border

The fear of ISIS and of Ebola has been fused with the controversy over immigration and over border crossings from Mexico. Large numbers of Americans believe that Islamist terrorists and people carrying the Ebola virus are crossing the border. There is no evidence whatsoever to back up these fears, but they persist, as did fears a decade ago that Arab terrorists were going to invade from the south. These fears are grounded in Americans’ own peculiar nativism, which contrasts the purity of the New World with the evil of the Old. That perception goes back, of course, to the American Revolution, but it has regularly been updated to include the latest threat from abroad.

Laura Murphy, a professor of English at Loyola University in New Orleans, has described some of this history. The outbreak of deadly influenza in 1918 was blamed on immigrants. The Irish were blamed for cholera, and Jews for tuberculosis. Last July, as the controversy over Central American children raged, Georgia Representative Phil Gingrey, who, believe it or not, is a physician, wrote the CDC, "As you know, the United States is currently experiencing a crisis at our southern border. The influx of families and unaccompanied children at the border poses many risks, including grave public health threat. … Reports of illegal migrants carrying deadly diseases such as swine flu, dengue fever, Ebola virus, and tuberculosis are particularly concerning."

These fears of ISIS and Ebola have spawned a much different politics from the fears created by September 11. September 11 contributed to George W. Bush’s popularity and to his re-election in 2004. As Solomon, Greenberg, and Pyszczynski demonstrated, morality fears generally encourage support for charismatic politicians, or father-figures. By this logic, one might think that the crises over Ebola and ISIS would accrue to Barack Obama’s political favor and increase his popularity, as Americans look to him to save them from these threats. But in this case, the opposition has been able to exploit these fears to further disapproval of Obama and his presidency. 

The post has been updated.