Septicemic plague is a severe form of the plague caused by the bacterium Yersinia pestis. It occurs when the bacteria enter the bloodstream, leading to a rapid and serious infection. Symptoms can include fever, chills, weakness, and abdominal pain. If not treated quickly, it can be life-threatening. This type of plague can develop from untreated bubonic plague, where the bacteria spread from the lymph nodes to the blood. Septicemic plague can also occur without any prior symptoms of bubonic plague. Prompt medical attention and antibiotics are crucial for recovery and to prevent complications.