The first well-reported epidemic of the Black Death was the Justininan Plague that devastated 6th century Europe. But the disease may have arisen thousands of years earlier in ancient Egypt, according to a new theory. The banks of the Nile were the perfect place for the four key players in the disease--humans, black rats, fleas, and the plague bacterium Yersinia pestis--to get together, says archaeoentomologist Eva Panagiotakopulu of the University of Sheffield, U.K.
The black rat--which spread the devastating pandemics--originally hails from central Asia, but no one is sure where it acquired the oriental rat flea Xenopsylla cheopis that hosts the plague bacteria. Many researchers think that the rodents arrived in the eastern Mediterranean already carrying bacteria-laden fleas. In a paper in the February Journal of Biogeography, Panagiotakopulu says that it's more plausible that the flea's original host was the Nile rat, Arvicanthis niloticus. That species has strong immunity to plague, so rodent, flea, and bacterium could have coexisted comfortably throughout prehistory without transmitting the disease to humans.
Some 5500 years ago, Panagiotakopulu notes, Egypt became cosmopolitan. Humans started living in towns, making it easier for diseases to spread. Later, international trade arrived, and black rats arrived on newly established trade routes from India and Mesopotamia. The river's annual flood would have driven Nile rats into town, where they could have shared their fleas with black rats. Unlike the Nile rat, the plague bacterium kills black rats quickly, leaving lots of hungry fleas looking for a home--and surrounded by humans. And once black rats hosted the oriental fleas--and with it, Y. pestis--they spread the plague across entire continents, she says. (Because fleas can also go for a month without feeding, they could also have spread in cloth or grain.)
Although plague was not an epidemic disease in ancient Egypt, papyrus manuscripts from around 1500 B.C.E. describe patients suffering from diseases with similar symptoms, such as buboes and black spots, says Panagiotakopulu. Those symptoms don't convince Mark Spigelman, a paleopathologist at the Hebrew University of Jerusalem, Israel, who notes that they could be from leprosy or tuberculosis. "It's a nice theory--no doubt there were rats and fleas in the Nile," says Spigelman. "But whether these people suffered from plague is uncertain."