A year ago something terrible happened in London’s Oxford Circus.

It was just after peak hour on Friday, November 24, 2017, and hundreds of thousands of people were in the city center to take advantage of the Black Friday sales. The problem started underground, and news passed quickly through the masses, sweeping up through the subway tunnels and into the streets. Alarm turned into panic, and panic became fear and eventually outright terror, crackling like wildfire through the crowded streets.

Within minutes, thousands of shoppers were stampeding, dropping their bags, dialing loved ones, and ducking low behind hastily barricaded department stores. Emergency services leapt into action, throwing up fencing and evicting crowds from nearby streets. The London Fire Brigade was called, while social media filled with rumors of gunshots and videos of screaming crowds fleeing the station entrance.

Singer Olly Murs, locked inside Selfridges at the time, urged his more than eight million Twitter followers to get out, if any were inside.

Londoners’ worst fears had been confirmed. In a city primed for terror, it was a familiar feeling. Memories were fresh of attacks on Westminster Bridge, parliament, on London Bridge, at Borough Market, and on the tube at Parson’s Green. As one onlooker described afterward, “What went through my mind immediately was ‘It’s Black Friday in Oxford Circus in a city that’s had incidents,’ and as I ran, I was too terrified to look back because I thought I would see a car heading towards us.”

Our preprogrammed physiological reactions to danger can be triggered by a tweet.

Except there was no car.

There was no incident.

No terrorist attack, no bomb.

An inquest later found that the whole thing had begun with a scuffle on the platform for the Central Line. The panic, chaos, speculation, and misinformation rippled out from there. Because the crowds had been packed in so tightly, nobody could see or hear what happened. Each person picked up on the fear of the person next to them, and it became scarier the farther it traveled from the epicenter.

Nobody had information. All they knew was that it was one of the busiest days of the year, in a country that’s a terrorist target, in a city that’s a terrorist target, in a shopping area that’s an obvious target. The fear fed on itself, multiplying and spreading like a virus or pandemic—eventually shutting down parts of one of the world’s biggest cities.

Humans are really good at picking up emotion in other humans.

We’re able to detect the tiniest changes in another person’s expression, in the modulation of their voice or the tensing of their shoulder muscles. Emotion is its own language, and stress, anxiety, and fear are some of the strongest “words.”

We speak that language from an early age. Researchers at the University of California, San Francisco, found that when infants are cradled by their mothers who have just experienced a socially stressful event, the infants’ heart rates go up too. The message transferred from a mother’s pounding heart is danger, and the baby responds without needing verbal cues. That ability sticks with us for life. If your co-worker is stressed, you are more likely to tense up and feel stressed yourself. It’s infectious; you’re picking up on body language.

You don’t even need to be in the same room or the same country. Studies show that reading bad news or seeing videos of something scary raises your pulse, makes you sweat, and dilates your pupils. Our preprogrammed physiological reactions to danger can be triggered by a tweet. That’s why the Oxford Circus panic was so bad: It was amplified by social media.

Fear can be transmitted digitally as easily as it can physically—and that’s a problem because digital technologies reach everyone. It’s not a few thousand people in a crowd anymore. Three-quarters of adults on earth now have a smartphone, which means we’re getting 24-hour access to all the worst stories happening everywhere to 7.6 billion people—all the time.

The speed and tenor of cultural conversation is now mind-bogglingly fast. The moment something bad happens somewhere on the planet, fear ripples through the ether. One person armed with a bad story can infect millions of others in a few minutes. That’s why, right now, the English-speaking world is in the middle of a fear pandemic.

Every day terrifying stories sweep through the global village, in articles, tweets, and evening broadcasts, and they are amplified a million times over until there’s nowhere to hide. Algorithmic bias, mental illness, foreign infidels, chronic pain, hooded extremists, robots coming to take our jobs, burning forests, warlike naval maneuvers, marching racists, rising waters, surveillance regimes, trade wars, toxic chemicals, predatory capitalism, roaming gangs of criminal youths, drug overdoses, benefit-devouring migrant caravans massing at the border… the list goes on and on. The fear virus takes hundreds of forms and mutates and spreads every time we click or watch or mutter darkly about the future at family dinner.

Danger, it turns out, is a relative concept rather than an absolute one.

At times, it feels like we’re helpless against the onslaught. Cognitive biases leave us ill-equipped to deal with the nature of the digital plague. Amygdala hijacks and warped media business models are just the tip of the iceberg. Recency bias means we give more weight to stuff we’ve heard recently: The latest cholera outbreak feels typical, but we forget about the UNICEF time series showing that global deaths are on the decline. The availability heuristic causes us to give more weight to things that are easier to imagine. After decades of priming by news broadcasts and Hollywood thrillers, it doesn’t take much effort to picture that lone gunman rampaging through a school or the journalist ambushed and murdered at an embassy.

We’re discovering new cognitive biases all the time too. There’s one known as “concept creep,” uncovered by Daniel Gilbert at Harvard and Nick Haslam at the University of Melbourne. If we’re looking for danger and it then disappears, we seek out new, lesser forms of danger to replace it. In one study, Gilbert’s team of researchers showed volunteers a series of computer-generated faces and asked them to decide which seemed threatening.

As they showed fewer and fewer threatening faces over time, the volunteers expanded their definition of threatening to maintain a similar number. Eventually, in a sea of smiling faces, even a slight frown seemed scary. Danger, it turns out, is a relative concept rather than an absolute one.

As David Levari explains, there’s a good reason for this. Our brains have evolved to conserve energy, and relative comparisons use less energy than absolute measurements. It’s a lot easier to remember which of your cousins is the tallest than to remember how tall each cousin is. Whenever it can, our brain uses these kinds of rules of thumb because that’s usually enough information to safely make decisions while expending as little effort as possible. Concept creep is a great example of this in action. The human watcher will evaluate faces as threatening long after they have ceased to be so or identify the slightest scuffle as the sign of a terrorist attack if primed by the news to be on the lookout.

Perceived threat also triggers a stress reaction that makes us better at processing information that conveys unrelated bad news. A series of brain imaging studies by neuroscientists in New York, for example, have shown that unexpected signs of danger trigger a neural signal that switches on the learning part of our brain that makes us better at retaining information. When firefighters have had a few hectic days in a row, they’re far more likely to predict there’s a chance they could be involved in a car accident or become a victim of credit card fraud. It doesn’t matter that these have nothing to do with fires. The world just seems like a more dangerous place.

In 2018, we’re all in the same boat. We’ve become really good at identifying the bad things happening all around us. Every time we catch the fear “virus,” it leaves us more susceptible to the next outbreak. We’re living like firefighters on call—constantly ready to put out the flames in our news alerts and on our social media feeds. The unrelenting messages of doom travel through the information superhighway in the same way the panic spread through the crowds at Oxford Circus—terrifying people, causing further panic, making everyone more likely to watch out for more trouble, and creating a permanent state of anxiety.

Here’s the real problem: By almost any measure, the world is becoming a better place. The large scale evidence for this has already been well documented by people such as Max Roser, Steven Pinker, and the late, great Hans Rosling. Poverty is disappearing, battle deaths are falling, violence is less common, suicide is decreasing, life expectancy is increasing, literacy is on the rise, child mortality is declining, we’re making great strides in battling diseases like AIDS, cancer, and malaria.

The internet has democratized information, education, and business; it’s given voice to the silenced, helped to erode outdated taboos, and advanced human rights. Of course, it’s not all perfect and there are always setbacks, but every day, the human species is making incredible progress.

There’s a strange, sad irony in this. We’ve never had it so good, and yet we’ve never been more scared. Just as we’ve reached the point in our evolution where we can see ourselves as we truly are, see the evidence of both the terrible things we’ve always done to each other and the evidence of our progress in making those things happen less often, we’ve also managed to spook ourselves into a state of abject terror.

That’s why the fear virus is so pernicious. It’s as if we’ve been huddled in a cave for millennia, waiting for the storm to pass. And just as it’s starting to taper off, we’ve stoked the fire, made the shadows dance higher on the walls, and retreated even further into the dark.

We can’t afford to do that because there’s a long road ahead. Not all the news is good: the 21st century has brought a series of new challenges (and a few old ones) into full view: Populism, ecological collapse, economic inequality, accelerating climate change, poverty, war, hunger, disease, and intolerance are still with us. We need to continue throwing everything we’ve got at these dangerous issues.

A healthy respect for the scale and magnitude of these challenges is important because it creates awareness and the basis for a common understanding. That’s what allows us to work together. But when awareness tips over into unnecessary fear, when the virus becomes so virulent that it causes us to panic, we stop. Fear immobilizes us and keeps us from seeing countervailing forces, positive stories, and emerging solutions. It causes us to confuse the growing pains of change with signs of the end of entire systems. It makes us miss the possibility that behind the end of the old ways there might be new ones poking through.

A terrified populace is far more susceptible to the appeals of people who want to make countries great again and demagogues who see politics as a zero-sum game. A terrified populace is less willing to stand up and fight for an economy that doesn’t cost the earth.

But there is something we can do: Don’t let the fear virus get you.

When the stories reach you, don’t “cough” and pass them on. Every time you do that, you become another victim, infecting your friends, your family, and your followers. Make sure the fear virus stops when it reaches your doorstep.

Instead of being a vector for stress and outrage, be a vector for optimism and progress. In the panic at Oxford Circus, it would have taken only a few hundred people to stem the tide by keeping calm and carrying on. Stop panicking, reduce the anxiety of those around you, give everyone the gift of time to think and evaluate—the opportunity to make better decisions.

In all this, remember that every step we take is the mark of a species willing to challenge itself and press forward, seeking out wonder, identifying problems and solving them. We have the ability to look inward by looking outward. Take time to enjoy the successes and celebrate them. Kill the fear in its tracks. Replace it with new narratives about how our best natures can overcome our worst: how the goodwill, cooperation, and kindness of humans can overcome the wickedness, self-deception, and greed.

The poison, as always, is also the cure.