Your husband's case is concerning for a possible infection. I agree that he should have some routine blood tests drawn such as a complete blood count to look at the number of white blood cells (marker of infection)and an electrolyte panel along with blood and urine cultures. Although he may not have " signs of kidney problems" he could have a urinary tract infection that has spread into his blood stream. WIth this severity of headache and fever, he should be thoroughly evaluated for worst possible case scenarios such as meningitis so that nothing is missed. Call your doc ASAP for further advice or take him to the ER for the labs and a more extensive exam. Make sure they know about the persistent headache and fever. If the neuro exam shows neck stiffness or other worrisome neurological signs, he may need a CT scan of the brain and maybe spinal tap. Good luck.