What 3 centuries of smallpox mortality data shows about how epidemics linger

Researchers pored over weekly reports of deaths in London to get a centuries-long view of how and when smallpox outbreaks ravaged the city.

(CNN)As so many people around the globe contemplate what their lives might look like after the pandemic, new research on smallpox might help provide insight.

Researchers revealed nearly three centuries of data showing repeated smallpox epidemics in London in a study published Monday in the open access journal PLOS One.
"This study reveals detailed patterns of extremely important infectious disease, over a very long period -- much longer than any human lifetime," said lead study author David Earn, a professor of mathematics at McMaster University in Hamilton, Ontario.
    The smallpox story is a sobering reminder of a not-too-distant reality: The monthslong wait for the expedited Covid-19 vaccine pales in comparison to centuries in which smallpox was rampant.
      "Smallpox was ... staggering in comparison to what we're talking about now. I mean, there's just no comparison of the level of devastation and fear this disease caused," he said.
      With the help of his colleagues and undergraduate research assistants, Earn -- over the course of the last few years -- digitized 13,000 weekly smallpox mortality records.
      "I've looked at annual counts of smallpox, but not these weekly counts and the weekly counts reveal the full structure of the epidemics, how fast each epidemic took off exactly," Earn said. "The shape of the epidemic curve was completely hidden before this."

        Hundreds of years of data

        Left untreated, smallpox would kill three out of every 10 who were infected with it, according to the Centers for Disease Control and Prevention. And those who survived often lived with scars afterward.
        The new study follows research Earn has published on the historical spread of diseases such as bubonic plague, cholera and scarlet fever.
        His team's goal was to make these records publicly available and enable scientists to analyze how patterns of disease spread in populations. Many historic trends can alter disease spread. Natural forces, such as the weather or the changing of the seasons, can drive an outbreak.
        And then there are social factors: population density, population structure, the introduction of schools and the course of wars.