Bubonic Plague

In humans, plague can take two forms. One form, called the bubonic form, usually results from a flea bite and is characterized by a sore called a bubo. The bubo is actually the infected lymph node that drains the area through which the bacteria was introduced by the infected flea. The lymph node enlarges and turns black. Other symptoms of this form of plague include fever and congestion of the blood vessels of the eye. As the disease progresses, the bacteria spread to other parts of the body, resulting in septicemia, or widespread infection. The fatality rate of the bubonic plague is 15%.

In another form of plague, called the pneumonic form, the bacteria infect the lungs. This form of plague can follow the bubonic form, as the bacteria spreads to the lungs. Or, a person may simply contract the pneumonic form only, and show no evidence of a bubo. The pneumonic form is highly contagious and especially virulent: the average length of time from the first appearance to symptoms to death is less than two days.

For both types of plague, antibiotics can cure the disease. A vaccine is also available to protect those who are at risk of contracting plague. People who work with Yersinia pestis in laboratories and in environments where wild rodents are infected with the bacteria usually are vaccinated against plague. United States soldiers who fought in the Vietnam war in the 1960s and 1970s were vaccinated against plague. However, the vaccine only protects against the bubonic form, not the pneumonic form. People who are exposed to the pneumonic disease should take antibiotics as a precautionary measure.