What disease is primarily caused by Yersinia pestis?

Yersinia pestis is the bacterium responsible for causing the plague, a severe infectious disease that historically led to pandemics and significant mortality rates. The plague can present in several forms, with the most common being bubonic plague, which is characterized by swollen and painful lymph nodes called buboes. There is also septicemic plague, where the bacteria invade the bloodstream, and pneumonic plague, which affects the lungs.

Understanding the historical significance of Yersinia pestis is crucial, as it was the causative agent of the Black Death in the 14th century, a devastating pandemic that changed human history. This bacterium is typically transmitted to humans through the bite of infected fleas or direct contact with infected animals.

While pneumonia is listed among the options, it is not primarily caused by Yersinia pestis but may occur as a complication of pneumonic plague. Syphilis, caused by Treponema pallidum, and tuberculosis, caused by Mycobacterium tuberculosis, are unrelated bacterial infections that do not involve Yersinia pestis. Thus, the primary disease linked to Yersinia pestis is indeed the plague, highlighting the importance of understanding its historical and clinical context.