An illness. (Cambridge Dictionary)
An illness, typically a minor one. (Oxford Dictionaries)
An ailment is an illness, especially one that is not very serious. (Collins Dictionary)
A bodily disorder or chronic disease. (Merriam – Webster)
Minor Ailment Scheme.
U.S. Recalls Americans From China to Investigate Mystery Ailment.
Illness similar to “attack” reported by diplomats in Cuba.