What causes an acute otitis media ear infection?

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.

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.


Continue Learning about Ear Disorders

Essential Facts About Ear Infections
Essential Facts About Ear Infections
While ear infections tend to affect kids—5 out of 6 children will experience this condition by the time they’re 3 years old—adults are not immune. And...
Read More
Should a child with an ear infection see a doctor immediately?
Manuel B. Torres Jr., MDManuel B. Torres Jr., MD
Typically, yes. An ear infection tends to be painful and produce fever. Small children who do not ha...
More Answers
How is an ear infection treated?
Ear infections may be treated conservatively with oral over the counter pain medication, or they may...
More Answers
All About Ear Infections
All About Ear Infections

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.