The U.S. Centers for Disease Control and Prevention (CDC) has confirmed that the outbreak of the pneumonic plague in the summer of last year was caused by the first known case of dog-to-human transmission of the disease.

The June 2014 outbreak, considered to be the largest one in the United States in 90 years, started when a middle-aged man brought an American pit bull terrier to a veterinary clinic, according to the report by the CDC.

The dog was suffering from drooling, jaw rigidity, fever and neurological problems. When its situation became worse, it was decided to euthanize the dog the following day.

Four days later, the owner of the dog came down with a fever and had bloody cough. He was admitted to a hospital for several days where doctors identified that he had been infected with the pneumonic plague. The patient was treated using antibiotics and recovered after 23 days in the hospital.

The CDC also confirmed that three other people had contracted the disease. They were all treated using medication.

What is the Pneumonic Plague?

According to the CDC, the pneumonic plague is caused by bacteria called Yersinia pestis, which often infects the lungs. The disease can easily be passed on from one person to another through the air, especially when someone inhales the aerosolized bacteria.

The Y. pestis bacteria can also be contracted through respiratory droplets such as when an infected person sneezes, drips, coughs or exhales. This form of transmission requires direct and close contact with the person or animal suffering from the disease.

The CDC warns that the pneumonic plague can be passed on by a person who is suffering from bubonic or septicemic plague. The bubonic plague is spread through bites from fleas infected with the Y. pestis bacteria, while the septicemic plague is transmitted similarly to the bubonic but without the buboes, or swelling of the lymph nodes.

If these illnesses are left untreated, the Y. pestis bacteria could also infect the person's lungs, resulting in pneumonic plague.

Typical symptoms associated with pneumonic plague are headache, fever and sudden weakness. People who reach later stages of the illness show signs of pneumonia, which includes chest pain, shortness of breath, cough and watery or bloody sputum.

After 2 to 4 days, the pneumonia worsens and may cause shock and failure of the lungs. It could also lead to death if not treated early.

Patients are treated using antibiotics within 24 hours after diagnosis of the initial symptoms in order to lessen the chance of death. Effective antibiotics against the disease are the tetracyclines, gentamicin, streptomycin, and chloramphenicol.

People who have had direct and close contact with an infected individual are treated with antibiotics for 7 days. They are also advised to wear a close-fitting surgical mask to protect them against transmission of the disease.

As of the moment, there are no available vaccines against pneumonic plague in the country.

In the United States, an average of eight people get infected by the disease each year, with most cases coming from Arizona, California, Colorado and New Mexico.

Photo: Kat Masback | Flickr