Imagine that you are in an outpatient clinic—general internal medicine. The patient is a 33-year-old man with a chief complaint of “I can’t get rid of this fever.” He had been in excellent health until two months ago. Since then, he has run fevers almost every day, usually in the range of 101 to 102 degrees Fahrenheit. He has also developed a cough that is getting increasingly worse and uncomfortable ulcers or sores in his mouth.