Etiology of Bubonic Plague

The plague is caused by a bacteria named Yersinia pestis. The most common type of plague is the bubonic plague and is spread through flea bites. The bubonic plague is not common in humans. The bacteria usually infects squirrels, rabbits and prairie dogs. People who handle these animals, especially if the animals are wild, are at risk of being bit by their fleas which are carrying the bacteria. The bacteria can also enter a cut in the skin of a person who handles an infected animal. Domestic cats that are allowed to roam outside can come in contact with wild animals with the bacterial infection and then spread it to humans.

People can get the plague when they are bitten by a flea that carries the plague bacteria from an infected rodent. In rare cases, you may get the disease when handling an infected animal.

A plague lung infection called pneumonic plague can spread from human to human. When someone with pneumonic plague coughs, tiny droplets carrying the bacteria move through the air. Anyone who breathes in these particles may catch the disease. An epidemic may be started this way.

In the Middle Ages in Europe, massive plague epidemics killed millions of people. Plague can still be found in Africa, Asia, and South America.

Today, plague is rare in the United States, but it has been known to occur in parts of California, Arizona, Colorado, and New Mexico.

There three most common forms of plague are:

• Bubonic plague -- an infection of the lymph nodes
• Pneumonic plague -- an infection of the lungs
• Septicemic plague -- an infection of the blood

The time between being infected and developing symptoms is typically 2 to 7 days, but may be as short as 1 day for pneumonic plague.

Risk factors for plague include a recent flea bite and exposure to rodents, especially rabbits, squirrels, or prairie dogs, or scratches or bites from infected domestic cats.