Compare this pattern of information flow to the way news spreads now. On Thursday, Craig Spencer, a New York doctor, was given a diagnosis of Ebola after presenting a high fever, and the entire world learned of the test result within hours of the patient himself learning it. News spread with similar velocity several weeks ago with the Dallas Ebola victim, Thomas Duncan. In a sense, it took news of the cholera outbreak a week to travel the 20 blocks from Soho to Fleet Street in 1854; today, the news travels at nearly the speed of light, as data traverses fiber-optic cables. Thanks to that technology, the news channels have been on permanent Ebola watch for weeks now, despite the fact that, as the joke went on Twitter, more Americans have been married to Kim Kardashian than have died in the United States from Ebola.

As societies and technologies evolve, the velocities vary with which disease and information can spread. The tremendous population density of London in the 19th century enabled the cholera bacterium to spread through a neighborhood with terrifying speed, while the information about that terror moved more slowly. This was good news for the mental well-being of England’s wider population, which was spared the anxiety of following the death count as if it were a stock ticker. But it was terrible from a public health standpoint; the epidemic had largely faded before the official institutions of public health even realized the magnitude of the outbreak.

We hear it said constantly that modern society is uniquely vulnerable to the threat of a pandemic because of the global connectedness of air travel. Yet we rarely pause to consider the other side of our global connectedness: the speed of information, which has been increasing at a much faster rate over the past few decades than the speed of airplanes has. With the H1N1 pandemic of 2009, for instance, a virulent new strain of the flu was identified in a rural Mexican community, and within a matter of days health organizations around the world had been notified, and were trained to identify the new virus.

Thanks both to technology and to the essential work of institutions like the World Health Organization and the Centers for Disease Control and Prevention, we can alert the world to potential threats from a single smartphone. This is particularly true in countries, like the United States, with mature public health institutions, but it is also true in countries like Nigeria that were able to act quickly on early information about Ebola victims and contain the outbreak within weeks.

So this is the strange paradox of the modern epidemic: The speed of information is both our greatest defense against a true epidemic in a city like New York, and it is the source of constant, nagging anxiety that creates the — entirely incorrect — sense that we live in unusually perilous times. A New Yorker or Londoner is far less likely to perish from an epidemic disease than he or she would have been 150 years ago. We are vastly less at risk and at the same time we are more worried — for the same reason.