For many people, infectious mononucleosis feels like a one-time illness: a few weeks of fever, sore throat, and exhaustion, followed by a slow return to normal life. But for a smaller group, joint pain arrives during the acute phase or lingers well beyond it, and most physicians have little to offer beyond "that can happen sometimes." That gap between what patients experience and what they are actually told is where this article is meant to be useful.

Cat scratch disease (CSD) is one of those conditions that rarely gets the attention it deserves. The textbook version — a cat scratch, a swollen lymph node, a few weeks of mild fever, then resolution — describes a real subset of cases.

O'nyong-nyong fever is one of those infections that sounds obscure until it affects someone you know — or until your own joints refuse to cooperate weeks after the fever has gone. Named from the Acholi language for "weakening of joints," this alphavirus illness swept through East Africa between 1959 and 1962, affecting an estimated two million people in what remains one of the largest mosquito-borne epidemics in recorded history.

Actinomycosis is not the kind of condition most people have heard of, yet for those living through it, the frustration is anything but abstract. It is a chronic bacterial infection caused by Actinomyces species — bacteria that are part of the normal flora of the mouth, gut, and female reproductive tract in virtually every healthy adult.