About 10 years ago, we packed up the car and dog and headed to a campground in Southern Colorado, only to be greeted by signs warning us of aggressive bears and bubonic plague in the area. Bubonic plague! We had thought the disease was wiped out in the Middle Ages, but we were quite wrong. Forget the wilds of Colorado; researchers this week reported that they found evidence of the plague in the New York subways.¹ Hartecollis, Artemona. “Bubonic Plague in Subway System? Don’t Worry About It.” 6 February 2015. New York Times. 10 February 2015. http://www.nytimes.com/2015/02/07/nyregion/bubonic-plague-in-the-subway-system-dont-worry-about-it.html

Bubonic plague is caused by the Yersinia pestis bacteria. The disease spreads when a rat or other small rodent gets infected with the bacteria and then becomes a host to fleas who then pick up the bacteria while feeding on the rat. The fleas hop off the rat and find a human (or domestic pet) host, bite, and voila! The plague spreads. But back to the subways!

The plague was discovered in New York when an investigation team from Weill Cornell Medical Center set out to create a microbial map of the subways. Creating such maps is part of an effort to understand more about the microbes that exist in public places, so that potential infectious disease outbreaks or even acts of bioterrorism can be spotted early.² Hotz, Robert Lee. “Big Data and Bacteria: Mapping the New York Subway’s DNA.” 5 February 2015. The Wall Street Journal. 11 February 2015. http://www.wsj.com/articles/big-data-and-bacteria-mapping-the-new-york-subways-dna-1423159629 As biologist Jonathan Eisen explains, “We know next to nothing about the ecology of urban environments. How will we know if there is something abnormal if we don’t know what normal is?”

And so, in an effort to discover what’s going on in the microscopic germ-world of New York, the researchers swabbed turnstiles, kiosks, benches, trash cans, railings and subway cars at 468 subway stations throughout all five boroughs in the City. After collecting more than 4200 DNA samples, they started sequencing and analyzing the specimens. So far, they’ve looked at about one-third of them. They’ve already found 562 species of bacteria, but most are harmless, with only 67 of those capable of causing illness. The quantities are so tiny that healthy people don’t need to worry about catching something from them. (It’s interesting to note that almost half of the species analyzed so far don’t match any known organisms, prompting the study authors to write that their findings “underscore the vast wealth of unknown species that are ubiquitous in urban areas.” It’s certainly interesting that even in these times of extraordinary advances, we still know zip about half of the organisms that inhabit our bodies.)

Anyway, back to the plague. Of the identifiable species, only a few raised eyebrows. First, the researchers found evidence of Anthrax. And then, there was the plague. The Anthrax, they figured, came from transporting domestic animals, although it’s been quite a while since chickens and cows rode the subways. Then, they found plague bacteria on a garbage can, a MetroCard vending machine, and a stairway railing. Since big rats frequent the New York subways with as much regularity as Wall Street traders frequent the stock market, it’s likely that the rodents carried the disease and deposited the bacteria there. The lead researcher, Dr. Christopher E. Mason, commented that they found “plenty of rat and mouse DNA” in their samples.

But the scientists assure the public that there’s nothing to fear. For one thing, the bacteria they found were dead.³ McNamee, David. “Why you do not need to worry about the bubonic plague in the New York subways.” 9 February 2015. MNT. 12 February 2015. http://www.medicalnewstoday.com/articles/289138.php For another, bubonic plague hasn’t infected any New York City denizen for 12 years. “The results do not suggest that the plague or anthrax is prevalent, nor do they suggest that NYC residents are at risk,” the researchers reported.

In spite of those assurances, The New York City Department of Health apparently feared that widespread panic would ensue, and so they issued a statement “strongly disputing” that either plague or anthrax traces actually were found. “We don’t know what bacteria they found, but it’s definitely not the plague,” said Levi Fishman, a department spokesman. “The interpretation of the results is flawed, and the researchers failed to offer alternative, much more plausible explanations for their findings. The NYC subway system is not a source of plague or anthrax disease, and the bacteria that cause these diseases do not occur naturally in this part of North America.”

In other words, if it shouldn’t exist, it doesn’t. If we don’t want it to exist, it double doesn’t. It kind of reminds one of the old joke–Denial is a river in Egypt–and is equally silly. In fact, tourists from New Mexico, where there is plague, carried the disease to the Big Apple in 2002. It’s more than possible that other tourists have ridden the subway since while carrying plague bacteria. But the Department of Health is correct in assuring the public that the plague is hardly a threat in New York. Even in the US West where live versions of the plague run free, only seven human cases of the disease manifest in a typical year.

It certainly is true that the plague was something to dread in the past. The disease wiped out an estimated 60 percent of the European population during the Middle Ages, leaving towns so devastated that nobody was left to bury the dead.⁴ “Plague.” Centers for Disease Control. 12 February 2015. http://www.cdc.gov/plague/history/   A later pandemic wiped out up to 69 percent of the Italian population in 1630 and then did nearly as much damage in Germany in the early 1700’s. Then there was another epidemic starting in China in the late 1800’s. One terrifying thing about the disease is that it kills victims in just a matter of days, after causing high fever and eventually respiratory failure. Another is that it’s unusually contagious.

Bubonic plague still exists in 20 countries. Now, there’s a controversial vaccine, and antibiotics can usually curtail the progression of the disease, lessening the threat somewhat, although there’s one form of the plague that can be difficult to control even with antibiotics, and people do still die from pneumatic plague. The other option, should bubonic plague resurface, is to go natural with “Thieves” essential oils.⁵ “Four Thieves Vinegar: Evolution of a Medieval Medicine.” 12 February 2015. http://www.secretofthieves.com/four-thieves-vinegar.cfm Thieves is a blend named for the thieves who were sentenced to dispose of the bodies of plague victims in the Middle Ages. The thieves somehow survived when everyone else around them succumbed, and it turned out that they had coated themselves with a blend of oils believed to keep away the disease.

While sceptics deny that thieves oil could possibly have offered protection against such a virulent disease, the fact is that nearly all versions of the blend–and there are many–include ingredients that might work to repel fleas. For instance, rosemary, cloves, citrus, eucalyptus, lavender, and garlic all are common ingredients both in natural insect repellants and in thieves blends.⁶ Naiman, Ingrid. “Four Thieves: Historic Anti-Plague Remedy.” Kitchen Doctor. 12 February 2015. http://www.kitchendoctor.com/essays/four_thieves.php Also, thieves blends originally contained massive amounts of garlic, which we now know is a natural antibiotic. So in fact, the blend might well have protected those who applied it liberally enough or who drank small amounts of it.

Oh, and one other thing you can do to protect yourself is not sleep with your pet. That’s right, any pet such as a dog or cat that gets fleas is a potential carrier.

But there’s a lot more pressing stuff to worry about than protecting yourself against bubonic plague. Self-inflicted heart disease, diabetes, and cancer kill far more people every year than the plague ever did.