Greatest National Pneumonic Plague Outbreak in Nine Decades Started by Colorado Pooch

A small outbreak of plague that infected four humans and one dog in Colorado represents the first time that plague has been transmitted from one person to another in the US after 90 years, officials said Thursday, according to nbcnews.

The plague outbreak began with a sick pit bull. It transmitted the illness to its owner, a couple of vet techs as well as a close personal contact of the dog's owner, which all got infected. Ultimately, the dog died, but the others were healed with antibiotics.

As four men were infected at once, "this event represents the largest outbreak, and the first instance of possible human-to-human transmission, since an outbreak in Los Angeles in 1924," Runfola and colleagues write in the MMWR report, according to npr. "Hopefully, plague will not re-emerge as it did in the Middle Ages," says Dr. John Douglas Jr, the executive director the Tri-County Health Department, "but it's certainly endemic in rodent populations in the Western states, and it's something that those of us who live here will continue to encounter."

Usually, Yersinia pestis bacteria, the deadly plague carrier, is passed along flea bites. But the pneumonic form that impacts the lungs is caused by little droplets in a cough or through close contact.

 "We know that he got it from the dog. 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," the researchers wrote in a report circulated by the Centers for Disease Control and Prevention.

Last summer the dog fell ill, and then coughed up blood and became very weak. No one thought it was plague until its owner fell ill. At first, it was thought that he had got another bacterial infection, but later Yersinia pestis, the same bacteria that "wiped out 25 million people in the year 541 and tens of millions more throughout the Middle Ages" was detected.

However, plague still affects various parts of the world now and then. about eight human cases a year, is detected on average. "Plague is virtually always confined in this day and age to rural regions in the West," Dr. John Douglas, director of Colorado's Tri-County Health Department, told NBC News. "That is because the vector of plague is typically the prairie dog although there are other rodents that can transmit as well."

At first, when the Colorado health officials got the reports of plague, they began to investigate. The first human patient fell very ill, and was hospitalized. He could not talk, but the officials understood that his dog had become sick. Testing tissue samples in the vet made them detect plague.

"We know that he got it from the dog," Tri-County's Janine Runfola said. "He was coughing up blood. That is likely when some of the cases got infected, including the index patient."

Patients with pneumonic plague tend to cough out particles of infected blood and mucus that spreads to everyone around.

Being most dangerous, it is the only way that plague can get transmitted from human to human.

Even a couple of veterinary technicians got respiratory infection, so they doused themselves with antibiotics. After they realized that the owner had plague, they put on extra intravenous antibiotics to get healed.

"Don't let your dog run around where the prairie dogs are," notes Douglas. "If you live in the West and you live in places where there are rodents or you are hiking ... you need to be generally aware," Douglas said. Pets should get flea treatments and be kept away from wild animals. Don't let your dog run around where the prairie dogs are. Wear insect repellant and socks," he advised.