STATESBORO, Ga. -- What you think you know about the Black Death, which wiped out up to two-thirds of Europe in the Middle Ages, is wrong, say two Georgia Southern University professors.

Geographers Brian Bossak and Mark Welford theorize the epidemic wasn’t caused by bubonic plague, but instead was a virus spread by person-to-person contact along trade routes used mainly in warm weather.

They’ve published their ideas in the scientific journal Medical Hypotheses.

Theirs is a topic lots of people think they know a little about, Bossak said.

“Everybody is always interested,” he said. “There are universal accounts that everybody learns in school.”

And even though the epidemic peaked almost 700 years ago, some vestiges remain.

Bossak and Welford discovered their shared interest in the Black Death at a dinner for new geography faculty last fall. As the two professors chatted over dark beers, Bossak posed a few issues Welford had wondered about, too.

“The Black Death went so fast, but we knew bubonic plague in India in 1903 moved slowly, even with modern transportation,” said Welford, a native of Suffolk, England, where the epidemic hit especially hard.

“(Black Death) was whipping across Europe in two, two-and-a-half years.”

Black Death also peaked in the summer, while bubonic plague, which is carried by rat fleas, peaks in the winter as people congregate inside. How come there are no accounts of rats dying en masse as you’d expect with the bubonic plague? And why, the two wanted to know, did some areas of Europe avoid the disease altogether?

Bubonic plague became synonymous with the Black Death after a bacteriologist identified the bacteria Yersinia pestis as its cause in an 1890s Hong Kong outbreak. He then connected one of its symptoms - swollen lymph nodes or buboes - to historical descriptions of plague victims and concluded bubonic plague was what caused the Black Death.

“He made a leap,” Welford said. “We know now that a vast number of diseases cause the lymph nodes to swell. That should have made people wary. Rather than question it they tried to explain it away, which is not good science.”

Paradigms like this one are tough to break, Welford said, though scientists are trying. Just in the past decade, other researchers have also theorized the Black Death couldn’t have been bubonic plague. It’s clear to Welford and Bossak that the disease was viral, with a several-week-long incubation period during which the victim appeared healthy but could still infect others.

The geographers, along with three undergraduates, are building on previous work and testing their theory with GIS technology. Using church and civic records, they’ll compile and map as much data as possible about deaths in the epidemic. Onto that data they’ll layer what’s known about the location and size of both markets and roads at the time.

They expect to find that Black Death mortality peaks around major roads and large markets. Statistics will allow them to attach probabilities to their models.

They believe they’ll be the first to compile these records on a publicly available georeferenced GIS dataset, a kind of Google Earth for the Black Death.

It’s probably easier to sleep at night thinking we already know what killed off so many people in the Middle Ages and that we can control it now, Bossak said.

But it may be false security.

“Every civilization starts to adapt, then nature comes along with a plague or Malthusian havoc we’re not prepared for,” he said. “This gives us the possibility of preventing that in the future.”