What is pneumonic plague?

Pneumonic plague Plague is a disease caused by Yersinia pestis, a bacterium found in rodents and their fleas in many areas around the world. Pneumonic plague is a cousin of bubonic plague-the disease that scourged Europe in the Middle Ages-but the two have some important differences. Pneumonic plague can be transmitted from person to person; bubonic plague cannot. Pneumonic plague affects the lungs and is transmitted when a person breathes in Yersinia pestis particles in the air. Bubonic plague is transmitted through the bite of an infected flea or exposure to infected material through a break in the skin. If bubonic plague is not treated, the bacteria can spread through the bloodstream, infect the lungs, and later lead to pneumonic plague infection.

The World Health Organization reports that 1000 to 3000 cases of pneumonic plague appear worldwide every year.  An average of five to 15 cases appear annually in the western United States. Plague incidents are usually scattered and occur in rural to semi-rural areas, and most come from the bubonic form of the disease. Naturally occurring pneumonic plague is rare, but small outbreaks do happen. Both types of plague are easily controlled by traditional public health measures.

The cases of pneumonic plague could skyrocket if Yersinia pestis particles are released from an aerosol container during a bioterrorism attack. The use of bioweapons with these bacteria is plausible because the Yersinia pestis occurs in nature and can be isolated and grown in quantity in a laboratory. If used in an aerosol attack, the bacteria could enter the lungs of some people who would, in turn, infect others. Because symptoms may not appear for up to six days after infection, the infected persons could travel over a large area before becoming sick and contagious. This scattering of sick individuals could make controlling the disease difficult.

What are the symptoms of pneumonic plague?

People infected with pneumonic plague usually suffer fever, weakness and pneumonia with shortness of breath, chest pain, cough, and, occasionally, bloody or watery sputum. Other possible symptoms include nausea, vomiting, and abdominal pain. Without early treatment, pneumonic plague usually leads to respiratory failure, shock, and rapid death. Sick individuals transmit the disease through coughing and sneezing, and those standing within six feet of them can be infected.

If a patient's physician suspects pneumonic plague, he or she may take samples of the patient's blood, sputum, or lymph node aspirate and send them to a laboratory for testing. Once the laboratory receives the sample, preliminary results can be ready in less than two hours. Absolute confirmation will 24 to 48 hours.

How is pneumonic plague treated?

Pneumonic plague is curable if patients see a doctor and begin taking antibiotics within 24 hours of the onset of symptoms. Oral medications such as doxycycline and as ciprofloxacin can be effective in treating and preventing the disease.  Streptomycin or gentamicin antibiotics are appropriate for intravenous use. National and state public health officials have stores of these medicines, which would be distributed to the American population should a bioterrorism event occur.

Currently there is no vaccine for pneumonic plague, though researchers are working to develop one.

How can I protect myself from pneumonic plague?

If you are around someone infected with pneumonic plague, experts recommended that you wear a tightly fitting disposable surgical mask. If you don't have a mask, make a face covering out of layers of cloth. You should also seek antibiotic treatment quickly so you have less chance of developing the illness.

To find out more about pneumonic plague, check out the Centers for Disease Control web site, http://www.bt.cdc.gov/agent/plague/faq.asp, or ask your doctor.