Last week Sen. Rand Paul, a doctor, laid out the threat of Ebola in America thusly, to CNN:

"If someone has Ebola at a cocktail party, they're contagious and you can catch it from them.”

That statement is, of course, not true, unless the person is symptomatic, in which case he or she would not be up for hummus and chardonnay. But it’s not as untrue as what Georgia Republican Rep. Phil Gingrey, also a medical doctor, wrote to the CDC:

"Reports of illegal migrants carrying deadly diseases such as swine flu, dengue fever, Ebola virus, and tuberculosis are particularly concerning.”

If Gingrey were to consult a map, he might be relieved to find that West Africa is several thousand miles away from the U.S.-Mexico border. And that, Ebola being what it is, someone in the throes of the hemorrhagic fever would be unlikely to muster the strength to fly to Mexico and then sprint through the South Texas desert. More recently, Kaci Hickox, a nurse who recently returned to her Maine home after treating patients in Sierra Leone, was subject to an involuntary quarantine in a tent at a New Jersey hospital, despite not showing symptoms of Ebola.

It’s a big time of the year for fear. Not only is it Halloween, a holiday more recently known for sexy hamburgers but originally famous for its spookiness, but also because the U.S. has had four (now one) cases of Ebola diagnosed on its soil. Maybe it’s the combination of the two that helps explain the abundance of ridiculous statements like the above in recent weeks.

Call it Ebolanoia. A recent CBS poll found that 80 percent of Americans now think U.S. citizens who travel to West Africa should be quarantined upon their return, even though most health experts think that would only make Africa’s Ebola outbreak worse.

Of course, Ebola is partly a stand-in for our ongoing collective anxieties, ever simmering and child-leash-purchase inducing. In calmer times, we might instead be wringing our hands over gluten, swine flu, or that illegal immigrants are coming here to “steal our jobs.”

A recent survey from Chapman University found that Americans are most afraid of walking alone at night, identity theft, safety on the Internet, becoming the victim of a mass shooting, and having to speak in public.

The study also found that Democrats were most likely to be worried about personal safety, pollution, and man-made disasters. Republicans, meanwhile, had the highest levels of fear about the government, immigrants, and “today’s youth.” It also found that having a low level of education or watching talk- or true-crime TV was associated with harboring the most types of fear. Despite the fact that crime rates have decreased over the past 20 years, most Americans, the survey found, think all types of crime have become more prevalent.

Fear of things that might actually hurt us, like the flu or smoking, is understandable and healthy. It’s the phobia of things—snakes, sharks, the youth—that pose virtually no threat at all that’s more puzzling. (The last shark attack death in the continental U.S. was in 2012. Meanwhile, 30,000 people die in car accidents every year). Even in 2013, people thought more frequently about the possibility of a terror attack in the U.S. than they did about the prospect of their own hospitalization.

An inability to process these kinds of odds ratios is one reason why some people experience irrational, sometimes crippling, unease. In an interview with New York magazine about why Ebola is sparking mass hypochondria in the U.S., Catherine Belling, an associate professor at Northwestern University's Feinberg School of Medicine, chalked it up to a reasonable fear (you might get Ebola if you accidentally touch the bodily fluids of someone who has it) getting distorted by bad logic (you might get Ebola if you accidentally touch anyone, ever.)

“What hypochondria is, then, is the inability to put that very rational fear into context, where you can continue to function normally rather than being paralyzed by it," she said. "When someone who is in, for example, New York, won’t leave their apartment because they’re afraid of getting Ebola. They’re incapable of recognizing that there’s truly an incredibly minuscule likelihood of getting Ebola.”

There might be a vanishingly small risk of contracting Ebola in the U.S., but as Alicia Meuret, director of the Anxiety and Depression Research Center at Southern Methodist University, explained recently, “if someone is prone to being anxious, they will focus on that 5 percent or 1 percent that’s unknown.”

Unfamiliar things—immigrants and the Internet—tend to make us feel more afraid, as do things that have been mythologized as “scary.” Even scientists who study bugs have an irrational fear of spiders. The idea of instructional fear acquisition suggests that a child seeing her mother jump at the sight of a lizard can develop a new fear where there wasn't one. (One study found that newborns learn what to fear through the odor of their distressed mothers.)

“There’s a very special sense of horror that’s attached to Ebola, and before now, it’s been sort of alien,” Belling said. “And now it’s here. And I think that has captured imaginations in a scary kind of way.”

We also fear the unexpected—another attribute of America’s Ebola cases. That might be why nearly half of adults report being afraid of the dark, particularly those who are poor sleepers. People have even been shown to get more anxious when a harmless tone is sounded at unpredictable intervals.

Proximity plays a role, too. Just as Americans became more concerned about Ebola when it popped up in our hospitals, they’re more likely to support going after a hypothetical terrorist group when the group is presented as wanting to attack America, specifically.

We feel more imperiled when we feel physically vulnerable. People who think they are in poor health, regardless of whether they actually are, also feel like they are more likely to be victimized by criminals. The fear-mongering around Ebola on cable news is especially damaging because anxiety tends to breed more anxiety: The threat of contamination can lead to “mass psychogenic illness” in which people avoid things like gluten, vaccines, or windmills, simply because others do.

Finally, feeling like we’ve lost control is likely to bring out our worst phobias. As Madhukar Trivedi, chair of the University of Texas-Southwestern’s Mental Health Department, told KERA news, people are more afraid of flying than of driving cars because “in a car, at least I know when to brake. In a plane, I have no control.” He says people who fear flying find turbulence particularly terrifying: Is it just some choppy wind, or is it an engine malfunction? You don’t know, and there’s nothing you can do about it.

The downside of all of this is that being afraid can increase the risk of something bad actually happening.

“Sometimes when we’re afraid of something,” Christopher Bader, the Chapman sociology professor who led the fear survey, told the New York Times, “even if our fears are irrational, that can lead us to make choices that will actually cause the thing that we are avoiding.” Parks, for example, get more dangerous when people avoid them out of fear, because their emptiness encourages criminals to move in. In the case of Ebola, a travel ban or quarantine law would only hurt volunteer efforts in West Africa.

It also leads to a kind of maddening preposterousness, that, at best, makes us look back and cringe later. A school board in Stokes County, North Carolina, recently voted that an assistant principal will be required to work from home for 21 days after returning from a mission trip to Africa.

South Africa, that is.

"It’s not that we think that she poses any type of risk,” Sonya Cox, chairman of the Stokes County Board of Education, said. “But it's public perception here that we're concerned about.”