Black Death is Back: Second Plague Death Reported in Colorado

The Black Death is Back?


On August 5th, Colorado reported it’s second plague death in 2015 and the state has seen four human cases so far this year [1]. The two deaths in Colorado are the first deaths from plague in the United States since 2013, when a New Mexico man died [2-3]. The Colorado cases have all occurred in different counties, with the two deaths being in Pueblo and Larimer Counties [1,2,4]. Most recently, the city of Boulder reported its first plague case in over 20 years, after a man came in contact with a dead chipmunk in his yard [4].


However, Colorado is not alone in its plague affliction this year – California reported its first human case on August 6th. The case, a child from Los Angeles, is believed to have been exposed while camping in/around Yosemite National Park [6].  California closed the campground where the child stayed, and treated it with insecticide for four days before re-opening [5]. The California Health Department is now reporting that it will close a second campground for similar treatment after two dead squirrels tested positive for the plague [5]. Additionally, New Mexico has reported that a woman’s death in July is suspected to been a result of plague [5].


Animal cases have also been reported elsewhere in the country. In July, a prairie dog colony in Uintah County, Utah was wiped out by the plague [7]. Rodents in two locations in Idaho have tested positive this year [8]. As of May, New Mexico had already reported four cases of plague in animals, of greatest concern, the animals include a domestic dog and cat [9].


Noticing a geographic trend to all these plague cases?


Almost all plague cases, in both humans and animals, occur in rural areas of the western United States [10]. Interestingly, the division of plague-endemicity, or ‘plague line’ appears to clearly follow the 100th meridian [10]. The widely-accepted cause for this threshold being the boundary of prairie dog distribution [11].


But what is causing a notable increase in cases for 2015?


So far this year, Colorado has yet to surpass the eight human plague case-total from 2014 [12]. However, last year may not be representative of a trend for Colorado. As the Disease Daily previously reported, three of Colorado’s 2014 human cases were a result of occupational exposure to an infected dog and its owner, when the dog was brought in for treatment at a veterinary clinic [13]. Besides the pit-bull outbreak, Colorado has been seeing an uptick in cases – and officials are attributing it to climate [1]. The state has seen wetter winters and springs the past two years, which has lead to more lush vegetation and consequently, the possibility for thriving rodent populations [1]. A burgeoning rodent population means more hosts for the fleas that transmit plague, and increased likelihood that humans will come in contact with either.


In a 2012 report from the U.S. Geological Survey, instances where plague jumped from rodents to humans could be attributed to the wet winters of El Niño years [14]. Unfortunately the trend may not remain so straightforward, as it is unclear what could happen as climate change progresses [1].


















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