A report issued by the Centers for Disease Control Prevention highlights potentially the first human-to-human transmission of the pneumonic plague in almost a century and, according to state health officials, it was due to a pit bull in Colorado. Although the dog was humanely euthanized at a local veterinary clinic due to its symptoms, the four people involved, including the dog’s owner, two veterinary technicians, and a “close contact” of the dog’s owner, received adequate treatment and made full recoveries.

“Although human plague is rare in North America, it remains a public health concern in the western United States where Y. pestis circulates among wild rodent populations,” CDC researchers concluded in their research. “The risk for plague can be minimized by avoidance of possibly infected rodents (e.g., prairie dogs) and their fleas.”

Back in June 2014, a middle-aged man with no history of major illnesses developed a fever and cough that worsened significantly over the next 24 hours. After doctors diagnosed the man with pneumonia and prescribed antibiotics that had no effect on his condition, blood tests taken by the Colorado Department of Public Health and Environment revealed Yersinia pestis, the bacterium that causes the plague. An investigation led by Tri-County Health Department discovered the man’s 2-year-old pit bull was the root of the outbreak.

While the first human-to-human transmission of the plague since 1924 is certainly an interesting case, researchers confirm that the United States does not have to express concern over a Middle Ages-styled “Black Death” breaking out. The researchers are still trying to determine if the fourth patient involved in the outbreak, a close contact of the dog’s owner, transmitted the plague by being around the dog’s dead body or by being around the owner through his initial symptoms.

“All suspected or confirmed plague cases and rodent die-offs in areas where plague is endemic should be reported immediately to public health officials so that exposures can be minimized to prevent additional transmission,” researchers explained. “Once plague is suspected, appropriate precautions and treatment should be initiated immediately, and clinical specimens should be collected and tested as soon as possible.”

According to the CDC, the pneumonic plague can be spread from person to person by breathing in aerosolized bacteria. It can also be spread via inhaling Y. pestis that is suspended in respiratory droplets from a person or animal with the pneumonic plague. Initial signs of the plague include fever, headache, weakness, and fast-acting pneumonia. Pneumonia tends to progress two to four days and, left untreated, can result in respiratory failure and the patient’s death.

“Early recognition of plague, especially the pneumonic form, is critical to effective clinical management and a timely public health response,” the research team added. “Veterinarians should consider plague in the differential diagnosis of ill domestic animals, including dogs, in areas where plague is endemic.”

Source: Miller L, House J, Runfola J, et al. Outbreak of Human Pneumonic Plague with Dog-to-Human and Possible Human-to-Human Transmission — Colorado, June–July 2014. Morbidity and Mortality Weekly Report (MMWR). 2015.