The story of the Zika outbreak has been one of uncertainty, with constant new discoveries at every turn. The virus very likely causes neurological complications like Guillain-Barré and the birth defect microcephaly, for example, but scientists aren’t 100 percent sure. Just this month it has also been linked to inflammation of the brain and spinal cord. In February, it was discovered that it can be transmitted sexually as well as through mosquito bites. And the live virus has been found in a patient’s saliva, raising the question of whether it could be transmitted that way as well.

But for all Zika’s mysteries and surprises, we can safely say that it was not caused by genetically modified mosquitoes, that microcephaly cases aren’t a result of larvicides used to kill mosquitoes in water, and that the outbreak is not an attempt at population control by Bill Gates.

Still, these are all conspiracy theories that proliferate in certain sinkholes on the vast swamp of the Internet. But they’ve started to leach into the mainstream to a troubling degree. (Or some of them have—the Bill Gates one, thankfully, hasn’t gotten much traction.)

The genetically modified mosquito theory that seems to be everywhere has been attributed to a Reddit post. But the post led to a Daily Mail article with the headline “Are scientists to blame for Zika virus? Researchers released genetically modified mosquitoes into Brazil three years ago,” and a Fox News segment insinuating the same thing. There have been plenty of other articles on the theory since—debunking it, but still, it’s gotten enough attention now that there’s no stuffing it back in the Reddit cage. (Not good, especially considering genetically modified mosquitoes may be a key weapon in the fight against Zika.)

And the larvicide theory propagated by the Argentinian organization Physicians in Crop-Sprayed Towns grew loud enough to stop one Brazilian state from using the chemical in their water supply, and the federal Brazilian government was moved to dismiss the claims.

The outbreak, it seems, has created a breeding ground not just for the virus, but for conspiracy theories, which have hovered over the chaos of past epidemics as well. In 2014, for example, a Liberian newspaper accused the United States of using Ebola as a bioweapon. During the 2003 SARS outbreak, a couple of Russian medical experts speculated that the virus seemed to be man-made, which of course led conspiracy theorists down the bioweapon path again. And during the H1N1 outbreak of 2009, conspiracy theorists suggested that pharmaceutical companies caused it to reap a profit. (Conspiracy theorists had extra ammo in the vaccination campaign for H1N1. Let me tell you, anything involving vaccines opens up a whole new can of conspiracy worms.)

Is there something about these outbreaks of emerging diseases that makes them such fertile soil for conspiracies to grow in?

“There’s a group of people out there who have what we might call a conspiracy mentality,” says Joseph Uscinski, an associate professor of political science at the University of Miami, and author of American Conspiracy Theories. “[They] come up with conspiracy theories for everything that happens. There are a million conspiracy theories out there; most of them you will never ever hear of. The bigger or scarier an event seems to be, the more the conspiracy theories seem to come to the forefront. This is one of those cases.”

This is also why there are prominent conspiracy theories about JFK’s assassination, or 9/11. They’re big, scary events. And outbreaks are big, scary events that happen over a long period of time, providing ample opportunity for conspiracy theories to develop as researchers work to understand the disease and its spread.

With Zika right now, there’s an “informational void,” says Brendan Nyhan, an assistant professor of government at Dartmouth College. Scientists are working quickly to fill that void, but in the meantime, people still have questions that science just can’t answer definitively yet.

“When an outbreak happens, people understandably want to know where the disease came from and what governments and health agencies are doing to stop it from spreading,” Karen Douglas, a professor of social psychology at the University of Kent, told me in an email. “However, sometimes it's not exactly clear how governments and health agencies are responding, and sometimes messages from these sources are opaque, or full of scientific jargon that people don’t understand. When this happens, people become even more uncertain and scared. Research shows that these conditions provide fertile ground for conspiracy theories. People look for ways to deal with the aversive states of uncertainty.”

And feelings of anxiety and powerlessness —both things that have been linked to a tendency to believe in conspiracies—are plentiful in the Zika outbreak. While people who live in areas where Zika is spreading can use mosquito nets, and cover themselves in clothes and bug spray, ultimately they can’t control if they get it. And they may not even know if they do—four out of five people don’t show symptoms.

This wouldn’t be such a big deal were it not for Zika’s connection to serious neurological problems and birth defects. The symptoms of the infection are similar to a bad flu—fever, joint pain, headaches—plus a rash and red eyes. That alone probably wouldn’t be scary enough to get the gears of the conspiracy machine moving, and even it did, the media probably wouldn’t pay it much mind.

“There’s always going to be people saying things on the Internet that have no basis,” Nyhan says. “I think it’s appropriate to pull the alarm when it’s crossing over into public policy, into elected officials and pundits and commentators in mainstream media”—as it did when Sarah Palin talked about “death panels” or when the Brazilian state stopped putting larvicide in its water.

When people are exposed to conspiracy theories, this can perpetuate a cycle of powerlessness. Research done by Douglas and Daniel Jolley at Staffordshire University found that being exposed to anti-vaccine conspiracy theories made people feel more powerless, and also less likely to vaccinate.

The powerlessness that comes with thinking the government or doctors are up to something sinister is different than the powerlessness that comes with being at the mercy of nature. Conspiracy theories at least provide easy targets for blame—larvicides, genetically modified mosquitoes, the companies and governments that produce those things—rather than the capriciousness of the universe and the uncontrollable factors of an increasingly globalizing world.

“In some ways it’s more terrifying to confront a world in which your baby could be affected by something you have no control over,” Nyhan says, “[than] to live in a world in which people are pulling strings behind the scenes to cause these unpredictable threats.”