Final answer:
Yersinia pestis causes bubonic, septicemic, and pneumonic plague with symptoms like fever, chills, buboes, and pneumonia. Without treatment, mortality is high, but antibiotics substantially reduce death rates.
Step-by-step explanation:
Signs and Symptoms of Yersinia pestis Infection
The bacterium Yersinia pestis causes the bubonic plague, historically known as the Black Death. The transmission typically occurs through the bite of an infected flea. Symptoms of this disease manifest in various forms, categorized primarily as bubonic, septicemic, and pneumonic plague.
In bubonic plague, the incubation period ranges from 2 to 6 days, followed by sudden onset of high fever, headache, chills, and hypotension. One hallmark sign is inflamed lymph nodes, called buboes, which especially affect the groin due to the flea bites commonly occurring on the lower extremities.
Septicemic plague can result when Y. pestis enters the bloodstream directly. Symptoms include fever, chills, extreme weakness, abdominal pain, and shock, with potential complications such as disseminated intravascular coagulation (DIC), leading to thrombi and necrotic extremities. Pneumonic plague involves a rapid onset of pneumonia with symptoms like fever, headache weakness, and a productive cough, which can be fatal if not treated promptly. It is the form of plague that can be spread through aerosol droplets from infected individuals.
Without treatment, these forms of plague have high mortality rates, with bubonic plague leading to death in about 55% of cases and nearly 100% for septicemic and pneumonic plagues. With antibiotic treatment, mortality rates are significantly reduced.