Feedback
Science

New York Is Abuzz About Rats, Fleas and Plague … But Don’t Panic

Image: Rat

A rat scurries away in New York City. Matthew Frye / IPM / Cornell

Here's a gnawing problem.

Two scientific surveys of New York City's seamy side have turned up enough evidence of past and present pests to kick a hypochondriac into high gear — including rats with an unhealthy number of the fleas that could carry bubonic plague, also known as the Black Death, plus DNA traces of potential plague bacteria in New York's subway system.

But the biggest plague could well be the tendency to overhype common-sensical findings about the pathogens that surround us.

That's not to say New Yorkers should be unconcerned. Matthew Frye, an urban entomologist with Cornell University's New York State Integrated Pest Management Program, said a study focusing on the fleas carried by the city's rats underlines the importance of public health measures already in place.

"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," Frye said in a Cornell news release.

Rat on the loose terrifies NYC subway commuters 0:52

The study, published this week in the Journal of Medical Entomology, cataloged more than 6,500 fleas, lice and mites that were collected from 113 Norway rats. The rats were trapped over a 10-month period at five locations in Manhattan, including in three residential buildings.

Frye and his colleagues concentrated on the Oriental rat flea, which played a key role in the bubonic plague outbreaks that devastated Europe in the 14th century. About 30 percent of the rats had Oriental rat fleas, the researchers reported.

The scientists said that this was the first pest survey of its kind conducted in New York City since the 1920s. Back then, public health officials found that the city's rats had an average of less than one Oriental rat flea each — 0.22 fleas per rat, to be precise. This time around, the average was 4.8 fleas per rat, and at one of the sites, the flea index was 25.7 fleas per rat.

The good news is that none of the fleas actually carried the plague bacteria, known as Yersinia pestis — although some of them harbored potentially harmful strains of Bartonella bacteria.

A study published last month in the journal Cell Systems did turn up the DNA signature of Yersinia pestis — and anthrax bacteria, for that matter — among the thousands of species of bacteria present in the New York subway system. But those signatures were traced to dead microbes rather than active agents, and even then, there's some question about the potential for false positives.

The bottom line is that the low-level presence of such pathogens is probably part of "a normal, urban microbiome," the researchers behind that study said.

For more tips on pest control, check out this YouTube playlist

The published research papers lay out their findings in cool, dispassionate terms. Not so some of the reports spawned by the findings.

The subway study, for example, sparked this headline from the Daily Mail: "Terrifying Microbe Map of New York's Subway System Reveals Superbugs, Anthrax and Bubonic Plague." And the rat study brought this from Yahoo Health: "Grossest. Thing. Ever: New York City Rats Covered in Black Death Fleas." (Full disclosure: Our report has "rats," "fleas" and "plague" in the headline as well.)

The reality is that public health measures can head off New York's highly unlikely Black Death flea menace, as well as the all-too-real rat menace.

"In this age of modern medicine, I think New Yorkers are safe from an outbreak of plague," Frye reassured NBC News in an email. "That is because we have antibiotics that can effectively treat plague when it is recognized early. ... However, I think it is important that people take rodents more seriously as public health pests. Mice and rats living in someone's home should be viewed as a serious problem."

So what's to be done?

"Removing food and water and preventing access to shelter are key to knocking back rodent infestations," Frye said. He recommended a publication from the New York City Department of Health and Mental Hygiene, titled "Preventing Rats on Your Property." It's also important to get rid of the fleas, lice and mites that rats leave behind, Frye added.

If nothing else, the buzz over New York's rats — and the potentially dangerous pests they harbor — should serve as a wakeup call to get our own houses in order.

Update for 4 p.m. ET March 3: In response to NBC News' inquiry, the New York City Health Department sent along a statement that should make New Yorkers feel a lot safer when it comes to the Black Death:

"There has never been a case of locally acquired plague in NYC — or anywhere east of the Mississippi — in over 50 years. Additionally, no plague-infected rat has ever been found in NYC. Plague requires extreme circumstances besides fleas to pose a threat to human health, and those circumstances do not exist here."