Giant corporations, governments, and individuals are all making decisions that they hope will reduce the risk of spreading the new coronavirus — but not all of those tough calls are solely based on the latest health information. The factors that led people to enact two-week travel restrictions, or stock up on face masks, or cancel the Mobile World Congress are far more complex, and are based just as much on what scientists don’t know as what they do know.

Reactions to public health problems are mediated by more than just public health evidence or recommendations from public health experts. “It also depends on what other social and cultural influences are out there,” says Megan Jehn, who studies global health in the School of Human Evolution and Social Change at Arizona State University. “It depends on how different choices are framed or structured. The bottom line is, people are not making decisions based on empirical data.”

The World Health Organization declared the coronavirus outbreak a public health emergency of international concern. But at this point, the virus does not appear to be spreading widely in any countries other than China, which has the vast majority of cases. The WHO has not recommended that any groups cancel gatherings or meetings outside of China. In the US, the Centers for Disease Control and Prevention (CDC) continues to reiterate during press calls that face masks aren’t recommended. But cancellations and closings are piling up just as fast as face masks are flying off the shelves.

People make choices during epidemics based on how much risk they think the disease poses. The trouble is that there’s usually a significant difference between how the risk appears and the actual risk that they face. That perceived risk is influenced by a handful of factors, including the size of the threat, the types of information that they’re collecting on the threat, and the types of actions that other people are taking.

The threat posed by the new coronavirus is still unknown, which makes it seem more frightening than it actually might be. “That unknown risk makes it seem riskier,” says Gretchen Chapman, professor of social and decision sciences at Carnegie Mellon University. “Imagine you had two diseases that both had a three percent mortality rate, but one rate was ambiguous and could change, and the other was really certain. The one that had ambiguity would seem scarier.”

Information travels differently now than it did during epidemic outbreaks before the internet, and people seek out and believe disease information differently than they used to, says David Abramson, an associate professor at New York University’s School of Global Public Health. He says it’s much easier for misleading, inflammatory, or false information about this virus to take hold — like the dozens of conspiracy theories blossoming on social media. That, too, changes what people think about their risk from the coronavirus.

One key piece of information, though, is what people see their peers and those around them doing, Abramson says. “It’s often a predictor of what you will do,” he says. “If you’re walking down the street, and half of the people are wearing masks, you think, ‘should I be doing the same thing?’”

When companies, organizations, and governments are weighing their responses to disease outbreaks, their perceptions of risk are also influenced by politics and economics. Groups making decisions consider the appearances of actions, how accountable they would be if something bad happened, and the impact on their reputation that could cause. They also take external pressures into account: for example, multiple high-profile companies, like LG and Sony, backed out of appearances at the Mobile World Congress before the event was formally canceled.

The relative contribution of those factors to the decision-making process, compared with the weight of public health recommendations, depends on the specifics of each situation, Chapman says. “Maybe, on average, it makes people more aggressive in terms of taking action,” she says.

If the Mobile World Congress had gone on as planned, Abramson says it probably wouldn’t have put attendees’ health at increased risk, if precautions were taken — it was set to take place in Spain, which doesn’t have active spread of the virus. “They were being cautious and probably overreacting at the same time,” Abramson says.

The overreaction led to a decision that is based on recognized public health practices. Isolating people from each other and canceling mass gatherings can help to prevent the spread of active disease. But it’s only effective if there’s enough disease for it to be warranted, and only to a limit: for example, even though China shut down cities affected by the virus, it may have been too late to stop the spread by the time they put those measures in place. “Depending on how prevalent the disease is, it could be easy to over-apply these actions,” Chapman says.

Continued actions that aren’t in line with public health recommendations, like the ongoing travel restrictions, which the World Health Organization has objected to, might be done for other reasons if a group thinks that it is in harm’s way. “They could be doing it for other reasons, like to control panic,” Jehn says — and may see keeping their customers or attendees or citizens calm as an even more important goal.

The gap between how people perceive the risk of the coronavirus and how at risk they actually are will stick around until scientists learn more about what the actual risk is, and how well they can communicate it, she says. “And we still really don’t know how that will happen.”