Epidemiology
It is slightly more common in multiple births, in infants with chromosome anomalies, and in girls than in boys. References


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If the bacteria happen to enter the bloodstream rather than the lymph or lungs, they multiply in the blood, causing bacteremia and severe sepsis. In septicemic plague, bacterial endotoxins cause disseminated intravascular coagulation (DIC), where tiny blood clots form throughout the body, commonly resulting in localised ischemic necrosis, tissue death from lack of circulation and perfusion.DIC results in depletion of the bodys clotting resources, so that it can no longer control bleeding. Consequently, the unclotted blood bleeds into the skin and other organs, leading to red or black patchy rash and to hematemesis (vomiting blood) or hemoptysis (coughing up blood). The rash may cause bumps on the skin that look somewhat like insect bites, usually red, sometimes white in the center.Septicemic plague is caused by horizontal and direct transmission. Horizontal transmission is the transmitting of a disease from one individual to another regardless of blood relation. Direct transmission occurs from close physical contact with individuals, through common air usage, from direct bite from a flea or an infected rodent. Most common rodents may carry the bacteria and so may Leporidae such as rabbits:

Significant carriers of the bacteria in the United States include:
- Rats
- Prairie dogs
- Squirrels
- Chipmunks
- Rabbits
- Fleas
The bacteria are cosmopolitan, mainly in rodents in all continents except Australia and Antarctica. The greatest frequency of human plague infections occurs in Africa. The bacteria most commonly appear in rural areas and wherever there is poor sanitation, overcrowding, and high rodent populations in urban areas.