The phrase "occasional bout" refers to a temporary or occasional occurrence of something, usually referring to a short period of time when someone experiences a particular activity, illness, or behavior. Full definition
The symptoms can vary from mild lethargy or poor coat quality to severe skin allergies; from occasional bouts of soft stool or vomiting, to persistent, severe vomiting and diarrhea. (midislevet.ca)
My husband and I both suffer from occasional bouts with kidney stones. (globalhealingcenter.com)
Just as in humans, occasional bouts of diarrhea in cats are not totally unexpected. (cat-lovers-only.com)