Bubonic Plague

Cause and Effects

Plague is caused by infection with the bacteria Yersinia pestis, which infects small rodents and insects, usually fleas. Because pathogen survival depends on a specific animal population, plague tends to occur in the tropical, subtropical, and warmer temperate climates. Transmission to humans can occur through a flea bite as well as contact with infected people and animals. There are at least three forms of plague: bubonic, septicemic, and pneumonic; the different forms depend on how people are exposed to the bacteria.

Bubonic plague is so named after the painful bubo that appears after a bite from an infected insect. The course of illness is initially similar to many other diseases. Infected individuals usually show signs of illness within two to seven days of exposure to infection. The disease typically begins with nonspecific symptoms of fever, headache, and malaise. This may be followed by swelling of one or more lymph nodes, where the bacteria replicate, resulting in the bubo. The bubo is a unique feature of bubonic plague; it becomes quite painful and may become an open sore. The infection may spread to the bloodstream and/or to the lungs, resulting in septicemia and pneumonia, respectively. Septicemic plague results from the spread of a bacterial infection of the bloodstream without the initial appearance of a bubo. Pneumonic plague is the most fatal, but fortunately the least frequently seen form of this illness. Individuals with plague pneumonia are contagious; other individuals can become ill through inhaling infected droplets. Rare cases of plague result in meningitis and throat infections. Persons with suspected plague are treated in isolation to prevent spread of the disease.

[Page 39]Plague is treated with antibiotics. Aminoglycosides (streptomycin and gentamycin), chloramphenicol, and sulphonamides have been used effectively in treating human plague cases. Other antibiotic classes may not be as effective. In addition to antibiotic treatment, patients may require general supportive care, depending on the severity of illness.

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