The phrase "nasty bout" refers to a difficult or intense episode or experience of something negative, usually related to illness or conflict. Full definition
Do not give your kitten cows milk, doing so is not good kitten care, not only is it unnecessary it can cause nasty bouts of diarrhea. (best-cat-art.com)
Winter finally caught up with the Memphis suburbs over the past couple of weeks, bringing nasty bouts with freezing rain and (currently) a little snow. (cbr.com)
The result of consuming bitter zucchini can be a very nasty bout of diarrhea, tummy ache and vomiting. (homemade-baby-food-recipes.com)