According to a new study in the Journal of Medical Entomology, New York City’s rats are host to a flea that has been associated with the bubonic plague and the Black Death.

Over the course of 10 months, researchers from Cornell and Columbia studied 133 rats from five different areas in the city, and found that they carried around 6,500 fleas, mites and lice. Among the well-known types was the Oriental rat flea, the flea known for its role in transmitting the aforementioned deadly diseases. Before you freak out, though, know that none of the fleas found contained the actual plague.

In fact, the discovery may help researchers understand how the disease spreads. “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,” said Michael Frye, the study’s lead author.

New York has not seen a human case of the plague in 12 years, according to the CDC. If you want to keep that streak going, here’s some advice from the study’s authors:

The study’s results suggest that public health officials closely monitor city rats and the fleas that call them home. But everyone can contribute, Frye says, by implementing IPM practices. “Removing food and water and preventing access to shelter are key to knocking back rodent infestations,” he says.

When we evict rats from our homes and workplaces, we need another core IPM practice – careful sanitation. It’s critical to rid buildings of the fleas, lice and mites that are left behind. “It’s not that these parasites can infest our bodies,” Frye says, “but they can feed on us while seeking other rats to infest.”

(Photo: Arturo Vidich)