The recent detailing of the 4-person cluster of plague cases that occurred in Colorado in 2014 is a fascinating look at how plague, in the modern age, can still cause substantial morbidity.
People forget that plague is endemic in parts of the US that are west of the "plague line" and we have a handful of cases each year in the US. What was special about this cluster was the involvement of a dog and possible human-to-human transmission in one instance. Additionally, half of the cases of pneumonic plague were mild and didn't require hospitalization, a fact that calls into question the common conception of plague as a universally severe illness.
The index mammal in this outbreak was a dog who was euthanized for an illness that caused bloody-tinged cough. This was subsequently diagnosed as plague and the property on which he lived had inactive prairie dog burrows and rabbits--known means for how the dog may have acquired its fatal affliction.
What happened next illustrates the concept of One Health, an approach to medicine and public health in which animal and human health issues are integrated, perfectly: 3-4 contacts of the dog became ill with plague. Of the 4 human cases, 3 had very close contact with the ailing dog and the remaining patient had some contact with the dog but also close contact with the dog's owner, raising the prospect that human-to-human transmission occurred--a phenomenon that hasn't occurred in the US for 70 years.
So, it's time to add spreading plague to the long litany of things, including their favorite pastime of eating homework, to blame on dogs