Learn English – figure of speech for “illlness which passes without a special treatment”

In German we have a figure of speech: "Das geht von selbst vorbei", which normally means that an illness will pass without the need to treat it with medicaments or something special at all.
Is there a similar figure of speech known in the English language, too?

Edit:

Because I'm trying to translate a joke I will share it with you, too. Perhaps you could figure out a better way of translation (I doubt that it would be worth to be a question of its own):

Two planets chat:
"How are you?"
"Not so good; feelin' miserable!"
"Oh? What's up?"
"I have Homo sapiens..."
"Nah, don't worry: it will run its course!"