Background. AOM usually occurs concurrently with, or just after, a viral upper respiratory infection (URI). It is generally believed that viruses play a role in the pathogenesis of AOM by causing eustachian tube dysfunction, which leads to invasion of bacteria from the nasopharynx into the ME. We have previously shown that many respiratory viruses can also invade the ME and that viruses enhance the production of inflammatory mediators induced by bacteria in the ME. In this study of children with AOM and a documented, concurrent viral URI, we sought to determine whether the rates of ME invasion are different between common respiratory viruses.

Methods. Between 1989 and 1993, 463 children (aged 2 months-7 years) with AOM were enrolled in various antibiotic trials. At enrollment and after 2-5 days on antibiotic therapy, middle ear fluids (MEFs) were obtained for bacterial and viral cultures and respiratory syncytial virus (RSV) antigen detection. Nasopharyngeal lavage specimens for viral culture and antigen detection of respiratory viruses were also collected at both visits. The viral etiology was further determined by serologic studies on paired serum samples drawn at enrollment and 9-12 days later.

Results. The specific viral etiology of the infections was confirmed in 185 (40%) children, who had a total of 207 viral infections (18 children were infected by 2 viruses, and 2 children by 3 viruses). During these 207 documented viral infections, the infecting virus was detected in the MEF in 98 (47%) cases. The highest rate of ME invasion was observed with RSV(54/63, 86%; P<0.001 vs. all other viruses). Also, parainfluenza(15/29, 52%) or influenza (10/24, 42%) viruses were found in the MEF significantly more often than enteroviruses (3/27, 11%) or adenoviruses (1/24, 4%; P<0.05). Other viral infections detected in the children were cytomegalovirus (32), rhinovirus (4), herpes simplex virus (3) and untyped hemadsorbing virus (1).

Conclusions. The rates of ME invasion during AOM varied significantly among the respiratory viruses; RSV showed a particularly strong capability for ME invasion. These differing rates suggest that while some viruses may enter the ME passively along with nasal secretions, other viruses may actively invade the ME and contribute to the inflammatory process in the ME mucosa. Because antibiotic treatment of AOM does not eradicate viruses, their presence in the ME may also have an impact on the resolution of AOM.