When plague came to the English village of Eyam 350 years ago, it wasn't rat fleas that infected the majority of people with the deadly bacteria, but rather human-to-human transmission, a new study finds.
From 1665 to 1666, the villagers of Eyam heroically quarantined themselves with the hopes of protecting people in neighboring villages from catching the deadly disease. During the 14-month quarantine, entire families died, said study senior researcher Xavier Didelot, a senior lecturer of epidemiology at Imperial College London.
In all, 257 of the 689 villagers died of plague, historical records show. But the fleas that live on rats infected just 25 percent of those people, the new study found. The other 75 percent caught plague from the bites of fleas and lice that normally live on people, or (less commonly) from contact with bodily fluids from sick people, the researchers found. [Pictures of a Killer: A Plague Gallery]
The high amount of "human-to-human route of transmission is surprising," Didelot told Live Science in an email. "It was previously assumed that most cases of plague were due to transmission from rodents via their fleas, which is a completely different species from the human flea."
Didelot got interested in the Eyam quarantine during a recent family vacation to the village. "Like most people visiting Eyam, I became fascinated with the story of the 1665-6 plague outbreak, and how the villagers bravely quarantined themselves," he wrote.
Together with his co-researcher Lilith Whittles, a doctoral student also at Imperial College London, he collected all the available data on the Eyam quarantine. The researchers looked at who had died of the plague and when. And they built a statistical model to show the time periods over which people who are infected with the plague become infectious to others, and then eventually die, Didelot said.
The model showed that human-to-human transmission explained the majority of the plague deaths.
The researchers also found that the village's children and those who were poor were at increased risk of the disease. Wealthy people lived in cleaner conditions, and likely had less social contact with other adults than those with less money, they said. But children of all classes often play with lots of other children, including some who may have been sick with plague, they said.
In addition, fewer people died in the winter. This is possibly because there were fewer rats then, but it also might be because people tended to stay indoors and interact less with others, the researchers said. [7 Devastating Infectious Diseases]
By the time plague reached Eyam, it had been pandemic in Europe for three centuries. None of the treatments at the time were very effective, but people had realized that some measures — including quarantines — helped stem the spread of the disease, Didelot said.
It was another 200 years before the plague's cause — the bacterium Yersinia pestis — was discovered in 1894, he said.
But although the quarantine may have helped Eyam's neighbors, modern antibiotics that treat the disease make the quarantine a strategy of the past, Didelot said.
"We do not suggest that our study should inform modern practice," he said.
The study was published online Wednesday (May 11) in the journal Proceedings of the Royal Society B: Biological Sciences.