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Should we be worried about the plague?

by Matthew McDonald

California’s Depart­ment of Public Health and Yosemite National Park announced last week that a child con­tracted the plague after vis­iting the park in July. The case was the third in the U.S. to be reported in recent months and, while the child in Cal­i­fornia is recov­ering, two people in Col­orado died from the dis­ease ear­lier this summer.

Though the plague is not new to the U.S.—reportedly arriving in 1900—it is rare. According to the Cen­ters for Dis­ease Con­trol and Pre­ven­tion, on average, seven human plague cases are reported in the U.S. each year.

With the plague’s recent return to the news, we took a look at some myths and truths about the centuries-​​old dis­ease and spoke with sta­tis­tical physi­cist Alessandro Vespig­nani, the Stern­berg Dis­tin­guished Pro­fessor of Physics, Com­puter Sci­ence, and Health Sci­ences at Northeastern.

The plague is gen­er­ally trans­mitted through human-​​to-​​human contact.

[MYTH] According to the World Health Orga­ni­za­tion, the plague is an infec­tious dis­ease caused by bacteria—Yersinia Pestis—that is usu­ally found in small ani­mals and their fleas. The dis­ease is trans­mitted by the bite of infected fleas or, less fre­quently, through direct con­tact with infected ani­mals, such as rats or squirrels. Human-to-human trans­mis­sion typ­i­cally requires direct con­tact with a person with pneu­monic plague. Such a case has not been doc­u­mented in the U.S. since 1924.

[EXPERT] Vespig­nani: “Direct con­tact with infected ani­mals or humans and, more rarely, aerosol inhala­tion or the con­suming of con­t­a­m­i­nated food are other routes of trans­mis­sion. In areas where plague is endemic in the animal pop­u­la­tion, it is good to avoid small rodents, avoid direct con­tact with poten­tially infected ani­mals, and use flea control products.”

In the U.S., the plague is most preva­lent in the western part of the country.

[TRUTH] According to the CDC, human cases in the U.S. gen­er­ally occur in rural regions of northern Ari­zona, Cal­i­fornia, southern Col­orado, western Nevada, northern New Mexico, and southern Oregon. Since 1970, only one case of human plague has been reported east of Texas.

[EXPERT] Vespig­nani: “San­i­ta­tion and pest con­trol have made urban out­breaks very rare. In the U.S., the last was in 1924. Plague needs an animal reser­voir, and now it is lim­ited to rural areas, espe­cially in semi-​​arid regions.”

The plague is untreat­able and often results in death.

[MYTH] For cen­turies, this was the case. But with modern med­i­cine, the plague, though a very serious ill­ness, is treat­able with com­monly avail­able antibi­otics. According to the CDC, in the pre-​​antibiotic era, mor­tality resulting from the plague in the U.S. was 66 per­cent. By 2010, that rate decreased to 11 per­cent. For cen­turies, the plague caused wide­spread panic and remark­able mor­tality rates. There have been three recorded plague pan­demics, from the Jus­tinian Plague in the early Middle Ages, to the “Black Death” or Great Plague that swept across Asia, Europe, and Africa begin­ning in the 1300s, to the Modern Plague that spread to port cities around the world in the late 1800s and early 1900s.

[EXPERT] Vespig­nani: “If diag­nosed early enough, the plague is treat­able with antibiotics. This is obvi­ously a game-​​changer with respect to what hap­pened during the Great Plague, where no cure nor under­standing of the trans­mis­sion mech­a­nism were available.”

Vespig­nani on the poten­tial for another pan­demic: “In 2013 there were little less than 800 cases of plague worldwide. Plague epi­demics are still pos­sible where the plague is endemic in an animal reser­voir. How­ever, the modern knowl­edge of the disease, prevention strategy, and the avail­ability of antibi­otics make large out­breaks extremely unlikely.”

Originally published in [email protected] on August 12, 2015.

Alessandro Vespignani: Fighting Diseases in the Age of Big Data

Alessandro Vespignani, The Sternberg Family Distinguished University Professor of Physics, Computer Science and Health Sciences

College of Science