• Fever of 102 degrees or higher
• Lethargy, irritability, extreme discomfort or pain
• Bloody or severe diarrhea
• Signs of dehydration, including dry lips and mouth, sunken eyes, rapid breathing or pulse, decreased urination and, in infants, a sunken fontanelle (soft spot), and/or a lack of urination for six hours
• Vomiting that lasts more than two days, or more than several hours for infants