An 18-month-old boy is brought by his mother with a two-day history of increasing irritability and poor feeding. For the past 24 hours, he has had a fever, has been waking frequently at night crying, and has been tugging at his right ear. There is no history of otorrhea, vomiting, or rash. He had an upper respiratory infection with a runny nose last week which resolved. His immunizations are up to date. He has been formula-fed since the age of six months and attends daycare three days a week.