Comparison of influenza A and influenza B virus infection in hospitalized children.

Background: Influenza A and B viruses were cocirculating in Australia in the winter of 1997.
Objective: To compare the clinical and demographic features of children with influenza A or influenza B virus infection admitted to a paediatric tertiary referral centre.
Methodology: Retrospective chart review of 91 hospitalized children with culture-proven influenza A or B virus infection during 1997.
Results: Thirty-six (56%) of 64 children with influenza A were under 12 months of age compared with seven (26%) of 27 children with influenza B virus infection (P = 0.02). Influenza B virus infection was more common in children with underlying medical problems (P = 0. 01). Neurological manifestations were present in eight (12.5%) of 64 children with influenza A and none with influenza B virus infection (P = 0.09). There were no significant differences in signs and symptoms of children with influenza A and B virus infection, in severity of illness or in duration of hospital stay.
Conclusions: A greater proportion of children admitted with influenza A virus infection were under 12 months of age. Influenza B virus infection is associated more commonly with underlying medical disorders. It is not possible to differentiate between influenza A or B virus infection from presenting clinical signs and symptoms.