Medieval cure-all may actually have spread disease.

One of medieval Europe's most popular concoctions for treating disease might instead have been an agent of germ transmission, new research suggests.

In the Middle Ages, merchants in apothecaries often dispensed mumia, or bitumen, a black, asphaltlike substance thought at the time to alleviate ailments as diverse as epilepsy, gout, and plague. When natural supplies of the oozing tar ran short, merchants turned to Egyptian mummies as a source of the material, says Barb'ra-Anne Carter of the California State University in Los Angeles. That's because the practitioners mistakenly believed that bitumen had been used to create the dark-skinned mummies, whose name derives from mumia, she notes.

When import restrictions interrupted the supply of Egyptian mummies, the European merchants--loath to give up a profitable product--turned to readily available local imitations. Slowly dried in ovens, these European "mummies" were made from any corpse that unscrupulous suppliers could get their hands on, says Carter. The remains of criminals, the poor, and the sick were favorite raw materials because they could be obtained more easily than other bodies could.

Apothecaries dispensed the freshly made mummies in several forms, including ground, powdered, and diced preparations. In some cases, they boiled the desiccated flesh and skimmed off the oils and resins that had floated to the top of the water. They sold this material in small flasks.

Carter speculates that people who consumed or applied European-produced mumia were being exposed to disease agents. Parasites can survive within recently dried fish, she notes, so human parasites could probably have remained viable within the European mumia.

Circumstantial evidence also suggests that some bacteria--including Yersinia pestis, the microbe that causes plague--might have found refuge in the mummies, she adds. Between 1720 and 1722, France experienced several outbreaks of plague, the largest of which occurred in Marseilles, a major mummy-making center.

Most researchers attribute the spread of plague among people to bites from rat fleas infected with Y. pestis because that's how the disease is usually transmitted today, says Carter. However, rat fleas are dormant in winter months, but the French outbreaks--as well as many European plagues of previous centuries--occurred in all seasons. Furthermore, there's scant documentary or archaeological evidence for inordinate infestations of rats during those outbreaks.

Maybe, Carter suggests, many European plague outbreaks were, in fact, a curse of the mummy.