Questions 4-5 are based on the following passage. A middle ear infection (otitis media) usually starts when a cold causes the Eustachian tube between the ear and throat to swell and close. When the tube closes, fluid seeps into the ear and bacteria start to grow. As the body fights the infection, pressure builds up, causing pain. Young children get more ear infections than adults because they get more colds, and their Eustachian tubes are more easily blocked. Symptoms of a bacterial ear infection include earache, dizziness, ringing or fullness in the ears, hearing loss, fever, headache, and runny nose. Children who cannot yet talk may tug on the ear as a sign of pain. Antibiotic treatment stops bacterial growth, relieving pressure and pain. Left untreated, the pressure can cause the eardrum to rupture. A single eardrum rupture usually does not have long-term consequences. However, repeated ruptures may cause hearing loss. 4. What does the passage mainly discuss?