Don't panic, we're told. The risk is low to most people. You don't need a mask unless you're sick or a health care provider. The common flu kills more people.

On the other hand: This thing is spreading. The deaths are mounting. The end is nowhere in sight.

As the number of cases and the number of places being infected by the novel coronavirus grows, everyone from Wall Street to the man on the street seems rattled. But how much of the fear is being driven more by emotions than facts?

SOME ANXIETY IS JUSTIFIED.

Experts in the psychology of risk perception - the study of the sometimes irrational and often emotional factors that determine what freaks us out and what doesn't - think that in the case of the coronavirus, we actually do have more to fear than fear itself.

"The risk is real, so let's put on the record right now that this is a concern," said David Ropeik, an expert on risk perception and communication.

"The challenge is keeping your worry in perspective, so you don't do something out of worry that's bad for you all by itself."

Ropeik has lectured at Harvard on risk perception and is the author of a book about how some of us worry too much about the wrong things How Risky Is It, Really?: Why Our Fears Don't Always Match the Facts.

He said there are a number of psychological reasons why the coronavirus crisis is triggering our fears a lot more than the flu, even though the flu, at least so far, has killed thousands more than the coronavirus.

FIRST OF ALL, IT'S NEW.

"When something is new, we don't know all of what we need to know to protect ourselves, and that feels like powerlessness. And that's what makes it scary," Ropeik said.

That's even though some of what's known so far about the disease doesn't sound too frightening.

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"If you look at the statistics, you might say, 'Well this is similar to the flu.' A bit more lethal, but it's low incidence. Most people, I mean 98 per cent or more, recover, often with a mild case. So what's the big problem?" said Paul Slovic, a psychology professor at the University of Oregon and an expert on decision making in conditions of risk.

But Slovic said, "When we see the pictures of the health care workers (responding to coronavirus outbreaks), they're dressed in hazmat suits and moonsuits. We don't see that with the flu."

A lack of control can be a big factor in what makes something scary or not, according to Slovic and Ropeik.

That's the reason why most of us aren't scared of driving, despite the risk of a fatal traffic accident, because we feel like we're in control behind the wheel.

But some of us are scared of flying partly because there's nothing we can do to shape the outcome of the flight. (Your lifetime odds of dying in a car crash is about one in 100, according to the US National Safety Council. The odds of dying as an airplane passenger is about one in 188,000.)

In the case of the coronavirus, we can wash our hands to try not to get it. But unlike the flu, currently we can't prevent it with a vaccine shot.

"That's very important for people. It influences people's sense of risk, whether or not they feel that they can control it personally by their actions," Slovic said.

Slovic said we can also try to protect ourselves by avoiding sick people. But it appears that the virus can be spread by people who don't appear sick.

"This undercuts our sense of control, if we can't even tell if someone is sick, if we should stay away from that person," Slovic said.

Lack of trust in the people informing us about the problem can also make us more afraid, according to the risk perception experts.

"It's not just half of the people who mistrust government. Half of them might mistrust this particular administration, but mistrust in government is very high," Ropeik said.

Inconsistent messages by politicians about the seriousness of the coronavirus outbreak have been a problem, Ropeik believes.

And mistrust in authorities can diminish their ability to keep us safe if, for example, we disregard orders to self-quarantine and that leads to a spread of the disease, Ropeik said.

The many things we don't know about the virus also is driving fears, Slovic said.

"We're told by the authorities that while we should be calm and keep this in perspective, they also admit they're still trying to learn more about this type of disease," Slovic said. "There's uncertainty, lack of control, fatalities, rising incidents, all of those things are worrisome. So it's not at all surprising that we're seeing such a strong reaction."

Sander Gilman, a psychiatry professor and medical historian at Emory University, said concerns about coronavirus has morphed into a moral panic, a term used by sociologists to describe widespread fear and anxiety of perceived societal threats ranging from Communism to violent video games to HIV.

It's the kind of fear that has led some people to stigmatise Asians or avoid Corona beer.

"This is a respiratory illness. If this were cholera, toilet paper would make sense," Gilman said. "My favourite example was an attack of graffiti on a restaurant in London, saying basically you're the cause of the disease and everything else. And it was a Japanese restaurant. All right? That's moral panic."

Ropeik said he can't tell people not to be afraid.

"Nobody can tell somebody else how worried they should be," he said. "That's a personal choice. Do you have kids? Are you old? Are you on chemotherapy? There's tons of factors."

But he said excessive worry comes at a cost, and not just to beer companies and Asian restaurants.

Worry equates to stress, and that can diminish your immune system, Ropeik warned.

"The worry alone is bad for your health," he said.