“Ring around the rosy, Pocket full of posy, Ashes! Ashes! We all fall down!” I’m sure everyone is familiar with Mother Goose’s darling verse, which has filled many a schoolyard day with mirth. However, the poem’s more sinister origins tell a story from a different time, one describing ‘rosy rashes’, ‘posy’ cures, cremation and even death. Certainly, if you look closely you’ll find that hidden within the innocuous rhyme lays the remnants of a medieval disease, the plague.

Perhaps the most historically significant microbe, the plague, has long been a thorn in the side of humanity. Responsible for three major pandemics, The Black Death, which occurred in Europe in the late 14th century is the most recognizable [5]. During this epidemic, over 50 million fatalities were recorded, which, at the time, was half of the entire European population [6]. Still, the last major outbreak was decades ago, causing many to write off this deadly pathogen, a potentially fatal mistake.

Although no longer causing Monty Pythonesque headlines, this bacterium is far from confined to the pages of history. In fact, the plague still garners a high body count in Madagascar, the Democratic Republic of Congo and Peru [4]. Even in a nation as medically advanced as the United States, the plague continues to be a problem [4]. This year there have been 15 recorded cases of the plague in America, up from 7 a year ago [4]. While a first glance, these numbers aren’t overly disconcerting at the very least the persistence of the plague is impressive and illuminates its medical relevance today.

Though, for the moment, the plague may be flying under the radar, it is still incredibly adept at its chosen craft, killing humans, one of the main reasons for its persistence today. So how does it work? Well, what is colloquially called the plague is actually the bacteria, Yersinia pestis [5]. What most people don’t know is there are actually three forms of the plague, bubonic, septicemic and pneumonic [2]. Each infects differential tissues types, lymph nodes, blood and lungs respectively [2]. Once inside, the bacteria cause fever, chills, weakness [2] and eventually death in 30-60% of individuals when left untreated [7]. More specifically, the success of Y. pestis is dependent on its ability to hijack human immune cells, using this machinery for protection and reproduction [5]. On its surface, Y. pestis expresses different virulence factors, molecules that act as keys allowing access to human white blood cells [5].

Fortunately, this scary disease has lost some of its bite, as the advent of antibiotics has armed humankind with the tools necessary to counteract its spread, reducing plague death by one third [3]. This is certainly good news, meaning a diagnosis is no longer akin to a death sentence. Even so, the plague has already claimed the lives of three Americans this year, [4] showing that antibiotics act only as a temporary fix, not a saving grace.

Even more distressing, to date no cure exists [2], due in large part to the way in which Y. pestis is spread. The plague is a zoonotic infection, which means it can be vectored between humans and animals [1]. In the past, the plague was carried to America from Europe on the backs of infected rats in the hulls of cargo ships [1]. Today, this problem no longer exists, however prairie dogs and ferrets have taken up the mantle of the most common carriers of fleas containing the Y. pestis bacterium [1]. This puts us humans between a rock and a hard place. We are unable to completely eradicate the plague, as long as these animal reservoirs exist to harbor it. Long term, vaccines are being talked about as a means to inoculate animal vectors against Y. pestis, [10] but they could be a long way off. So for the time being at least, it seems as if we are stuck together.

Where does that leave us? Based on the low levels of incidence, many Americans may go their whole lives without exposure to this burdensome beast from the past. This fact, coupled with the success of antibiotics treatment causes many pundits to turn a blind eye, ignoring the incredible deadly potential the plague retains. However, a disease, like the plague, which has proven to be historically lethal on several occasions [6], which additionally possesses adept invasion machinery, [5] should not be taken lightly, even in America.

Still, don’t take my word for it as today, in New York City the incidence of rat’s infestation has climbed to an all-time high [8]. The accumulation of these pesky invaders offers ample opportunity for Y. pestis to fester and spread, presenting a real and current danger [8]. So, is it time to panic now? Is the fourth pandemic upon us? Probably not, but it can’t hurt to keep a watchful eye trained on one of the deadliest diseases in human history. In the end, the carousel of life turns slowly round, blurring past, present and future. Let us heed the words of Mother Goose, finally bringing the plague from the shadows, ultimately preventing Y. pestis from once again causing us to all come falling down.

Works Cited

1.     Plague, Transmission and Ecology. Centers for Disease Control and Prevention; 2015. http://www.cdc.gov/plague/transmission/index.html

2.     Plague, Symptoms. Centers for Disease Control and Prevention; 2015. http://www.cdc.gov/plague/symptoms/index.html

3.     Plague, Diagnosis and Treatment. Centers for Disease Control and Prevention; 2015. http://www.cdc.gov/plague/diagnosis/index.html

4.     Plague, Maps and Statistics. Centers for Disease Control and Prevention; 2015. http://www.cdc.gov/plague/maps/index.html

5.     Connor MG, Pulsifer AP, Price CT, Kwaik YA, Lawrenz MB. Yersinia pestis Requires Host Rab1b for Survival in Macrophages. PLoS Pathog. 2015 Oct.

6.     Keeling MJ, Gilligan CA. Bubonic plague: a metapopulation model of a zoonosis. Proc Biol Sci. 2000 Nov; 267(1458): 2219-2230.

7.     Kugeler KJ, Staples JE, Hinckley AF, Gage KL, Mead PS. Epidemiology of Human Plague in the United States, 1900–2012. Emerg Infect Dis. 2015 Jan; 21(1): 16-22.

8.     Frye MJ, Firth C, Bhat M, Firth A, Che X, Lee D, et al. Preliminary survey of ectoparasites and associated pathogens from norway rats in New York City. J Med Entomol. 2015 Mar; 92 (14): 253-259.

9.     Thacker E, Janke B. Swine Influenza Virus: zoonotic potential and vaccination strategies for the control of Avian and Swine Influenzas. J Infect Dis. 2008 Dec; 17(Suppl 1): S19-S24.

Spencer Bigelow is a senior at Muhlenberg College (’16). He is currently working towards a B.S. in Biology and aspires to serve his country as a Naval surgeon. A former high school football player, Spencer enjoys spending his free time rooting for his hometown San Diego Chargers.