My Brother, Almost 80, Has Been Spiking Fevers Up To

My brother, almost 80, has been spiking fevers up to 103 & down for 48 hours. Initially,he had tremors & a sore throat; those have resolved, but not the fevers. He seems, when I heard him over the phone,to have some difficulty breathing. An urgent care dr. who examined him but took no x-rays, nor performed any tests, could find nothing.