New York City Rats, Fleas May be Carriers of the Bubonic Plague

If you are one of the 8.4 million people that live in New York City, be warned that researchers have discovered that the bubonic plague could be transmitted via rats.

The rats typically found in the subway host a species of flea capable of passing the plague, also known as The Black Death, to humans. However, plague itself has not been found in the rats or fleas in the study.

That's according to a study published this week in the Journal of Medical Entomology. It's the first study of its kind since the 1920s, researchers with Columbia University and Cornell University said.

"Despite finding traces of pathogenic microbes, their presence isn't substantial enough to pose a threat to human health. The presence of these microbes and the lack of reported medical cases is truly a testament to our body's immune system, and our innate ability to continuously adapt to our environment," wrote senior investigator Dr. Christopher E. Mason.

Researchers collected more than 6,500 fleas, lice and mites from 133 rats in New York City. Some 500 of those fleas were Oriental rat fleas, the kind that can spread the pathogens that cause the plague which killed millions in the 14th century.

"If these rats carry fleas that could transmit the plague to people, then the pathogen itself is the only piece missing from the transmission cycle," Matthew Frye, an urban entomologist with Cornell University's New York State Integrated Pest Management (IPM) Program, explained in a recent statement.

Frye said the three areas he studied - a residential building, a mixed-use building and an outdoor space - had different distribution levels of rats, fleas and bacteria, meaning more research is needed to see just where disease is hiding.

"We saw a tremendous amount of variation, and there's probably a lot more variation within the city," he said.