Menu

Human Fleas and Lice Spread Black Death

A new study suggests that the plague, which killed millions of people, was not transmitted by rats.

Jan 16, 2018
Ashley Yeager

Researchers have long thought that fleas on rats spread the Black Death during medieval times, but a new study suggests it was, instead, fleas and lice on people that transmitted the plague.FLICKR, BAYER CROPSCIENCE UKRats may have gotten a bad rap when it comes to the plague. It was fleas and lice on people, not rats, that spread the disease between the 14th and 19th centuries in Europe, according to a study published today (January 16) in PNAS.

The rodents have long been blamed for spreading the plague, which is caused by the bacterium Yersinia pestis. Researchers thought the bacterium would infect fleas on rats, and when the rats died, the fleas would jump to humans, infecting them. Rats are also thought to be responsible for spreading more recent cases of plague, including the outbreak in Madagascar in 2017.

But the long-held theory that rats spread the plague during the Second Pandemic in the 14th to 19th centuries had a problem—the disease did not spread quickly enough. This discrepancy spurred Katharine Dean, an ecologist at the University of Oslo, and her colleagues to study the patterns of how disease moves through a population. “The plague really transformed human history, so it’s really important to understand how it was spreading and why it was spreading so fast,” Dean tells National Geographic.

The researchers simulated the outbreak of the plague in nine European cities between 1348 and 1813. They modeled the spread of the disease by human fleas and lice, rat fleas, or transmission through the air. In seven of the nine cases, human fleas and lice best matched the pattern of outbreak, compared to the other two modes of transmission.

“The conclusion was very clear. . . . The lice model fits best,” study coauthor Nils Stenseth, a biologist at the University of Oslo, tells the BBC. “It would be unlikely to spread as fast as it did if it was transmitted by rats.”

The takeaway, Stenseth says: personal hygiene. The disease doesn’t spread if we stay clean. Another tip, he tells the BBC, “If you're ill, you shouldn't come into contact with too many people. So if you're sick, stay at home.” 

November 2018

Intelligent Science

Wrapping our heads around human smarts

Marketplace

Sponsored Product Updates

Slice® Safety Cutters for Lab Work

Slice® Safety Cutters for Lab Work

Slice cutting tools—which feature our patent-pending safety blades—meet many lab-specific requirements. Our scalpels and craft knives are well suited for delicate work, and our utility knives are good for general use.

The Lab of the Future: Alinity Poised to Reinvent Clinical Diagnostic Testing and Help Improve Healthcare

The Lab of the Future: Alinity Poised to Reinvent Clinical Diagnostic Testing and Help Improve Healthcare

Every minute counts when waiting for accurate diagnostic test results to guide critical care decisions, making today's clinical lab more important than ever. In fact, nearly 70 percent of critical care decisions are driven by a diagnostic test.

LGC announces new, integrated, global portfolio brand, Biosearch Technologies, representing genomic tools for mission critical customer applications

LGC announces new, integrated, global portfolio brand, Biosearch Technologies, representing genomic tools for mission critical customer applications

LGC’s Genomics division announced it is transforming its branding under LGC, Biosearch Technologies, a unified portfolio brand integrating optimised genomic analysis technologies and tools to accelerate scientific outcomes.