Final answer:
The nurse should prioritize inquiry about a history of a systemic infection within the past month, due to the concern for infective endocarditis considering the symptoms of fever, dyspnea, and a heart murmur.
Step-by-step explanation:
Given the young adult's presentation of fever, dyspnea, and a murmur, the nurse should prioritize inquiring about a history of a systemic infection within the past month. This priority is due to the concern for infective endocarditis, which can present with these signs and symptoms. Infective endocarditis can occur when bacteria or other infectious agents enter the bloodstream and take hold inside the heart, often following a recent infection. A murmur may suggest changes in the heart's function due to valvular issues that could be associated with or caused by infection.
While family history of coronary artery disease, recent travel to Third World countries, and pet ownership, especially cats with litter boxes, are important aspects of health history, they may be more relevant to other conditions. For instance, a recent travel history could suggest diseases common in specific geographic areas, such as tuberculosis or malaria. Pet ownership, particularly of cats, is associated with toxoplasmosis, which can present with fever but is less commonly associated with dyspnea or heart murmur unless there are underlying health issues or an immunocompromised state.