Yersinia pestis (the bacteria that causes plague) is often found in animals such as rats and prairie dogs. Bubonic plague transmission usually occurs through bites from infected rodent fleas, direct contact with infected tissue or bodily fluids, or inhaling infected droplets.
Fleas
Fleas

Between 1900 and 2010, 999 confirmed or probable human plague cases occurred in the United States. Over 80% of United States plague cases have been the bubonic form. In recent decades, an average of seven human plague cases have been reported each year (range: 1–17 cases per year) . Plague has occurred in people of all ages (infants up to age 96), though 50% of cases occur in people ages 12–45. It occurs in both men and women, though historically is slightly more common among men, probably because of increased outdoor activities that put them at higher risk.
Bubonic plague symptoms can occur within two to six days of being infected by the bacteria Yersinia pestis. If left untreated, symptoms, such as vomiting, abdominal pain, and diarrhea, can progress rapidly to septicemic plague. Approximately 10 to 20 percent of people with bubonic plague symptoms will also develop symptoms in the lungs. This is called pneumonic plague, and is often fatal.

Bubonic plague symptoms can occur within two to six days of being infected by the bacteria Yersinia pestis. If left untreated, symptoms, such as vomiting, abdominal pain, and diarrhea, can progress rapidly to septicemic plague. Approximately 10 to 20 percent of people with bubonic plague symptoms will also develop