This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'Which group of organism is responsible for transmitting endemic typhus? \nSelect and explain. \nA. Flea, B. Tick, C. Mite, D. Mosquito', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The etiologic agent of endemic typhus (murine typhus fever or fleaborne typhus) is Rickettsia typhi, a Gram-negative bacterium and obligate intracellular pathogen. Reservoirs include rats, mice, possibly other mammals, and infected rat fleas. Endemic typhus has a worldwide occurrence.', 'role': 'assistant'}]