Coronavirus has the world on edge.

The outbreak is now a global pandemic, and seven weeks after the first U.S. case was announced outside Seattle, the number of people in the U.S. now known to be infected with the new strain has surpassed 1,000, with 38 dead. And the numbers keep climbing.

Coast to coast, large public gatherings and major events have been canceled. Employees have been told to work from home, universities have moved all classes online and elementary schools have closed for sanitizing. The stock market has seen meteoric crashes. Declarations of emergency are being proclaimed, and New York has deployed the National Guard to the hard-hit city of New Rochelle, north of New York City.

As the number of confirmed cases of illness grows, so too does the nation's collective uncertainty. Psychologists and public health experts say public anxiety is high, and it's largely fueled by a feeling of powerlessness.

"When we feel, 'Oh my God, there's a new boogeyman out there,' it comes with extra fear," said David Ropeik, an expert on risk communication. "When we don't understand something that leaves us feeling like we don't know everything we need to know to protect ourselves ... that equates to powerlessness, vulnerability."

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The spread of the new coronavirus is not just a public health crisis. It's a global event pervading nearly every aspect of people's lives, causing them to worry not only about getting sick themselves but about Grandma's health, what to do with out-of-school kids, and how to absorb their rapidly shrinking 401(k)s.

Uncertainty about the nature and trajectory of the threat exacerbates a feeling of not being in control.

"It's a new, unknown illness, we don't know how severe it's going to be, and we don't know how concerned to be," said Lynn Bufka, associate executive director for research and policy at the American Psychological Association and an expert on anxiety, stress and cultural issues. "The idea that we can hopefully reduce transmissions through really good hand-washing feels insufficient. It's not anything new. And how will you know if you've done it well enough?"

It's why many people are rushing out to buy toilet paper, face masks, disinfectant and hand sanitizer. It makes them feel they are at least doing something, she said.

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Fear of the unknown

Part of what drives feelings of anxiety is a lack of information. The virus is new, and there remain many questions about the illness it causes. Most people haven't had it, nor do they know someone who has. Experts say that matters.

"We understand the flu, we have personal experience with it. That makes it less scary," Bufka said. "We know what to expect with something like that. As humans we can read information, hear information from others and take all that in, but personal experience makes a difference."

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Even as confirmed cases of the virus increase, the more people learn, the better they'll feel.

"We've filled in some of the blanks," Ropeik said. "We know who this affects. We know how it spreads. We know who is more vulnerable and who is less vulnerable. That knowledge is disinfectant."

A looming threat

David Clark, a clinical psychologist and author of "The Runaway Mind," said public fear may be heightened because of "looming vulnerability."

"When a danger or threat is gradually approaching it tends to be more frightening to us, than, let's say, if danger were to appear all of a sudden," Clark said of theory. "We started out with media reports from China which seemed to be very distant to us, not a particular threat, but then over the weeks we see this encroaching, getting closer and closer to home."

Now it's in the U.S., but not necessarily in everyone's state or community. As it expands, people remain anxious about if and when it will touch their lives.

Different people, different reactions

Not everyone reacts to epidemics the same way. Some people are cautious – washing their hands for the time it takes to sing two "Happy Birthdays." Some only one round. Others are stockpiling food and medicine as if an apocalypse were imminent.

Clark says that when news is mixed, people can choose to focus on the good or the bad.

The good news is, for most people, the illness caused by the coronavirus is generally mild and the flu-like symptoms of fever and cough don't last long. The bad news is the virus is novel and highly contagious, and right now there is no vaccine. The elderly and those with compromised immune systems or chronic diseases can become very sick and in some cases die.

Whether people fixate on the good or the bad has a lot to do with who they are.

"There are people who are particularly concerned about illness, disease – they feel a heightened sense of their own mortality," Clark said. "They're paying more attention to the bad news side of the messaging and probably having a harder time processing the good news side."

The appearance of mixed messages

That bad news/good news dichotomy can make people feel as though they are getting mixed messages. Reports say most people who contract the coronavirus experience symptoms similar to the flu. Then people read stories about the National Guard helping with quarantine containment.

If the risk to most people is mild to moderate symptoms, why does it feel as if the world is shutting down?

Public health officials are "trying to tamp down the infectivity curve," Ropeik said. "Think of it like the top of a big wave. They're trying to keep it from going up too sharply. If it goes up too fast and too high, the people who need health care will be crowding hospitals all at once, making it impossible for everybody who needs it to get care."

As President Donald Trump sought to reassure nervous Americans, some of his public statements also contradicted public health officials. He drew considerable fire last month for suggesting at a rally that the virus would take care of itself as spring approached.

"It looks like by April," he told supporters on the eve of the presidential primary in New Hampshire. "You know in theory, when it gets a little warmer, it miraculously goes away; hope that's true, but we are doing great in our country."

This week Trump's remarks took a marked turn when he said that the epidemic "blindsided the world," that the challenge was "not our country's fault" and that a "very dramatic" stimulus was needed to stanch plummeting markets.

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The role of the media

Health experts say the media has an important role to play. It must dispense accurate information without being sensational, and it must avoid exploiting people's fears. A blog post from the Poynter Institute, which trains journalists, noted that saying "deadly virus" can be misleading, because the virus is not deadly for most people.

People should also limit their media exposure, experts say. They caution against reading about the outbreak obsessively and recommend getting needed information and moving on.

"The best thing is to find some trusted sources, the outlets which are providing accurate information, and be cautious about social media," Bufka said. "You don't have to be constantly seeking information."

Bufka says that in times of uncertainty, people should strive for emotional balance. Maintain routines. Find someone who can help check fears and concerns. Don't talk frequently to the friend who's in a frenzy about it – fear, experts say, is contagious.

Why it may be OK that everyone is buying toilet paper

There isn't any real practical reason to stock up on toilet paper, but it may make people feel a bit in control of a situation rife with unknowns. Ropeik says that's important, because constant worry may make people more susceptible to the very thing they fear. Long-term stress is known to weaken the immune system.

"The more worried we are, the more vulnerable we are to this disease," Ropeik said. "The less worried we are because we bought toilet paper, silly as that seems, the more we've reduced our fear and minimized the effects on our immune system."

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Alia E. Dastagir is a recipient of a Rosalynn Carter fellowship for mental health journalism. Follow her on Twitter: @alia_e