Final answer:
The two stages of Y. pestis infection are the primary stage and the secondary stage. In the primary stage, the pathogen is transferred through flea bites and causes initial symptoms. In the secondary stage, the pathogen localizes in lymph nodes and forms buboes.
Step-by-step explanation:
The two stages of Yersinia pestis infection are the primary stage and the secondary stage. In the primary stage, Y. pestis is transferred to humans through the bite of infected fleas. This stage is characterized by an abrupt onset of symptoms such as fever, headache, hypotension, and chills. In the secondary stage, the pathogen localizes in lymph nodes, causing inflammation, swelling, and the formation of purple buboes.