Pneumonic plague occurs when the lungs become infected with the bacteria that cause plague (Yersinia pestis). This disease is most often transmitted when respiratory droplets from an infected person or animal are breathed in. It can also develop if bubonic or septicemic plague is left untreated. Antibiotics must be given within 24 hours of the first symptoms of this illness to reduce the chance of death.
Plague is an infectious disease that affects animals and humans. It is caused by the bacteria Yersinia pestis, which are found in rodents and their fleas. Plague occurs in many areas of the world, including the United States.
Pneumonic plague occurs when Yersinia pestis infects the lungs.
Yersinia pestis are Gram-negative bacteria. They are easily destroyed by sunlight and drying. Even so, when released into air, the bacteria will survive for up to one hour, although this could vary, depending on conditions.
Pneumonic plague is one of several forms of plague (see Types of Plague). Depending on the circumstances, these forms of plague may occur separately or in combination.
Besides pneumonic plague, the other types of plague are:
Pneumonic plague can spread from person to person through the air. Transmission can take place when someone breathes in aerosolized (gaseous) bacteria, as could happen in a bioterrorist attack. Pneumonic plague is also spread by breathing in Yersinia pestis that is suspended in respiratory droplets, from a person (or animal) with pneumonic plague. Becoming infected in this way, however, usually requires direct and close contact with the ill person or animal.
Pneumonic plague may also occur if a person with bubonic or septicemic plague is untreated and the bacteria spread to the lungs.