On Thursday, Nahid Bhadelia left rural Uganda, where she had been helping to set up a center for studying viruses such as Ebola. Before she left, she was peppered with concerned questions about when 2019-nCoV—the new coronavirus that has rapidly spread through China—would appear there. The virus had already reached 23 other countries, and when Bhadelia, an infectious disease physician at Boston University School of Medicine, arrived in Amsterdam on Friday morning for a layover, she noticed that a quarter of the people in Schiphol Airport seemed to be wearing face masks. When she landed in Paris for a second stop, she paused to deal with the barrage of tweets and emails that she had been getting about the new virus. “I’m not as worried by the disease as from people’s reactions to it,” she told me over Skype. “People are freaking out.”

The virus emerged in the city of Wuhan in December, and has infected more than 17,200 people. The large majority of cases have been in mainland China, but more than 140 have been detected elsewhere. At least 361 people have died in China, and one in the Philippines. In response, the World Health Organization recently declared a “public-health emergency of international concern” (PHEIC)—a designation that it has used on five previous occasions, for epidemics of H1N1 swine flu, polio, Ebola, Zika, and Ebola again. The invocation of a PHEIC is a sign that the new coronavirus should be taken seriously—and as the sixth such invocation in a little more than a decade, it is a reminder that we live in an age of epidemics.

Each new crisis follows a familiar playbook, as scientists, epidemiologists, health-care workers, and politicians race to characterize and contain the new threat. Each epidemic is also different, and each is a mirror that reflects the society it affects. In the new coronavirus, we see a world that is more connected than ever by international travel, but that has also succumbed to growing isolationism and xenophobia. We see a time when scientific research and the demand for news, the spread of misinformation and the spread of a virus, all happen at a relentless, blistering pace. The new crisis is very much the kind of epidemic we should expect, given the state of the world in 2020. “It’s almost as if the content is the same but the amplitude is different,” Bhadelia said. “There’s just a greater frenzy, and is that a function of the disease, or a function of the changed world? It’s unclear.”

Certainly, the new epidemic has grown at a pace unprecedented in recent history. The official case count has more than tripled within the past week, from about 4,500 on Monday to more than 17,200 now. In Wuhan, the number of ill people is straining the health care system, testing kits are in short supply, and hospitals are so full that some patients are being sent home to quarantine themselves, Amy Qin of The New York Times reports. The virus seems to have rapidly eclipsed SARS, which infected only about 8,100 people throughout eight months in 2002 and 2003.

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But several experts note that this comparison is misleading. SARS hit a world that was unaware of how far and fast a new virus could spread, and that was unprepared for such a threat. Many cases were likely never recorded because tests were slow to arrive and affected people weren’t sick enough to seek treatment. By stark contrast, the panic about the new coronavirus might lead to an uptick in known cases “because people are more conscious of it and are reporting their illness and seeking out testing,” says Angela Rasmussen, a virologist at Columbia University.

Diagnostic tests are already available for 2019-nCoV, even though the virus still lacks a formal name. In the U.S., the Centers for Disease Control and Prevention has already sent testing kits to state labs. In China, thousands of people are being tested every day, and that pace will only rise as two new hospitals finish construction. More testing means that, in addition to cases of very recent infections, doctors will start identifying people who had caught the virus earlier but hadn’t yet been diagnosed—a trend that inevitably leads to ballooning numbers. “It’s not that we’re getting this many new cases every single day,” says Maia Majumder, an epidemiologist at Harvard Medical School and Boston Children’s Hospital. The number of cases is rising because the medical system is not only playing catch-up to a virus, but also, reassuringly, closing the gap between infection and diagnosis.

But the number of new infections is rising. “We’re getting numbers faster, but that’s partly because there are more numbers,” says Tom Inglesby, a health-security expert at Johns Hopkins Bloomberg School of Public Health. “It’s not just an observation bias. It’s a real disease on the move.” And that movement is easier than ever: The number of people traveling by plane every year has more than doubled since SARS first emerged, in 2003.

The rate at which scientists can analyze a new threat has also increased dramatically. Zika spread through the Americas for 16 months before anyone even knew it was there. Ebola spread through West Africa for several months before any researcher managed to sequence its genes. But this time, in a matter of weeks, researchers recognized a new respiratory virus in the middle of flu season, identified it as a coronavirus, isolated it, sequenced its genome dozens of times over, and worked out how it sticks to human cells. “I’ve never seen anything like this before,” Majumder says. Researchers (and the WHO) have particularly praised Chinese scientists for their speed and transparency in releasing viral genomes and clinical data. China was heavily criticized for withholding and downplaying information during the SARS outbreak. This time around, “it’s a completely different ball game,” says Rebecca Katz, a health-security expert at Georgetown University. “There’s a tremendous amount of information being shared.”

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Despite that information, many unknowns remain. How transmissible is the virus? Once infected, how much time passes before people show symptoms, and how likely are they to die? Which people are most at risk? It seems that, on average, infected people spread the virus to two or three others. Thus far, only a minority of those who’ve been infected have become severely ill, and most of those people were either elderly or had prior medical complications. But there are still many uncertainties—and that is entirely normal. “These are the same questions you’d ask in every single outbreak ever—and given that this is a novel virus, we’re getting a lot of answers very quickly,” Katz says.

The unusual speed of discovery partly stems from better avenues for scientific communication. In the past decade, scientists have developed open portals for sharing and analyzing viral genomes, used preprint servers to quickly post new papers, and created rich networks on Twitter and other social media. Researchers can share data and refine ideas faster than ever—but they’re doing so in full view of a concerned citizenry. “You want the free flow of scientific information, but that information is being shared with the public at the same speed, while the scientific community is still digesting it,” Bhadelia told me.

Preliminary data that might once have run the gantlet of peer review before being published can now be downloaded by anyone, sparking misinterpretations and conspiracy theories. Epidemiological arcana, such as the R0 number, are suddenly the subject of widespread discussion. Uncertainties that academics are used to dealing with, about fatality rates or transmissibility, are stoking fear. “It’s not that we should know this by now and we don’t,” Majumder says. “What’s uncommon is not so much these epidemiological factors but the amount of public interest in them.”

Some of these dynamics were clear during the West African Ebola outbreak, in which misinformation and paranoia circulated faster than the actual virus (in part because of the man who now sits in the White House). If anything, the threat of misinformation is now worse, as false reports readily cascade through channels that amplify extreme messages over accurate ones. At a time when researchers are faster than ever at filling the information gaps that escort a new disease, those gaps can also fill just as quickly with bunk.

Hoaxes and half-truths are huge problems during epidemics. The worried well can overwhelm health-care facilities, and make it harder for medical providers to find and treat actual cases. Confused citizens might forgo sensible measures such as hand washing in favor of inefficient ones like panicked mask buying. And misinformation tends to intensify the xenophobia that emerges during epidemics. As diseases spread, “individuals find people to blame based on their prejudices, or make themselves feel less at risk by finding points of discrimination between themselves and others,” says Alexandra Phelan, who studies legal and policy issues related to infectious diseases at Georgetown University. Gay men suffered stigma and discrimination when HIV first emerged. Ebola became a stand-in for “any combination of ‘African-ness,’ ‘blackness,’ ‘foreign-ness,’ and ‘infestation’” during the West African outbreak, my colleague Hannah Giorgis once wrote. And now, as was the case with SARS in 2003, anti-Asian racism is rampant.

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In recent years, the world has seen a rise in anti-immigration rhetoric and isolationist politics, all of which are evident in the reactions to the 2019-nCoV outbreak. The State Department issued its highest-level travel advisory, warning Americans not to travel to China. Citizens who have recently returned from Hubei province are being quarantined. Noncitizens who have recently been to China will be denied entry. Such measures might seem intuitively sensible, but border screenings and travel bans have historically proved ineffective and inefficient at controlling diseases. If anything, they can make matters worse. “People will find a way to get where they want to go, but you lose the opportunity to provide them with information, and you drive them away from public health services,” Phelan says. “Measures that try to carve a country off from the rest of the world are deeply rooted in the protectionist approaches that have proliferated in politics. I think they make the world less safe.”

Bans can also break the fragile bonds of international trust that are necessary for controlling diseases, which is why the WHO advised against them when it declared a PHEIC. If countries know that they’ll be cut off during an epidemic, with all the economic repercussions that entails, they may be less likely to report future outbreaks, leading to costly delays. “The U.S. is a country with considerable normative weight internationally,” Phelan says. “And if a country knows that the U.S. is going to react like this, are they really going to come forward?” If China pays the price for transparency with 2019-nCoV, what lesson will it learn for the next epidemic?

And there will be a next epidemic. A new disease was always going to rear its head to test the world’s mettle, and more almost certainly will in the future. As I argued in 2018, the world isn’t ready. There has assuredly been progress—vaccines can be produced faster, global cooperation is tighter, basic research is nimbler—but supply chains are stretched, misinformation is rife, and investments in preparedness always fall into neglect once panic subsides. “Every year, things get more and more connected,” Inglesby says. “Epidemics like this show that all of it can be relatively quickly put at risk.”

Ed Yong is a staff writer at The Atlantic, where he covers science.