Diseases : Plague

Plague is an infectious disease caused by the bacterium Yersinia pestis, which is found in rodents and their fleas throughout the world. There are three types of plague : bubonic, pneumonic and septicemic.

Bubonic plague is the most common. Infection appears in the lymph nodes, causing them to swell and become painful. Infection results from the bite of an infected flea that has fed on an infected rodent, such as a rat.

Pneumonic plague is the most deadly form of plague but the least common. It occurs when Y. pestis infects the lungs. It can be spread through airborne droplets released through coughs or sneezes by a person or animal, especially a domestic cat, with pneumonic plague.

Septicemic plague can occur with either bubonic or pneumonic plague.


All forms of plague begin with flu-like symptoms. The first signs of illness are fever, chills, headache, weakness and muscle pain, and can include nausea, vomiting, diarrhea and abdominal pain. Pneumonic plague results in pneumonia that causes a cough producing bloody or watery sputum. The pneumonia progresses over two to four days and may cause septic shock and, without early treatment, death.


Several antibiotics can effectively treat plague. Early antibiotic treatment of pneumonic plague is essential. Preventative antibiotic treatment for seven days will protect persons who have had face-to-face contact with infected patients.

Further Information

Anyone with concerns or questions about human plague : please contact your physician or the staff of your local public health unit.


The information provided is subject to change. The information was collated from the following three sources :

1. Chin, J. "Control of Communicable Diseases Manual". 17th Edition. 2000. American Public Health Association: Washington D.C.
2. Health Canada website
3. Centers for Disease Control and Prevention website

*Advice on the most up-to-date treatment should be sought from a clinical expert.

January 2003

For More Information

Call ServiceOntario, Infoline at:
1-866-532-3161 (Toll-free in Ontario only)
TTY 1-800-387-5559.
In Toronto, TTY 416-327-4282
Hours of operation : 8:30am - 5:00pm

If you are a member of the media, call Communications and Marketing Branch at 416-314-6197 or visit our News Room section.

  • Connect With Us
Facebook Twitter YouTube RSS