What causes an acute otitis media ear infection?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Acute otitis media, or a middle ear infection, has several causes. When a child comes down with a cold, the infection causes the middle ear to produce fluid, which can collect behind the eardrum, resulting in a painful ear infection.

Sometimes the eustachian tube, which connects the nose and the middle ear, becomes clogged. This causes fluid to collect in the middle ear, which may be come painful and infected.

The third cause is infected and swollen adenoids, which are found in the upper part of the throat. The swollen, infected adenoids can block the Eustachian tubes and spread the infection to them.

Children are more susceptible to acute otitis media than adults because their immune systems are less effective at fighting infection. Also their eustachian tubes don’t drain as well as an adult’s because they are smaller and positioned more horizontally.


Acute otitis media (AOM) is often caused by bacteria, but can also be caused by viruses. The bacteria that usually cause AOM are Streptococcus pneumoniae (strep-toh-KOK-us KNEW-moh-NEE-ay), Haemophilus influenzae (he-MO-fill-us in-flu-EN-zay), and Moraxella catarrhalis (more-ax-EL-la ka-tar-HUL-iss). The viruses that most commonly cause AOM are respiratory syncytial (sin-SIH-shull) virus (RSV), rhinoviruses, influenza viruses, and adenoviruses.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.