Clinical presentation of influenza in unselected children treated as outpatients.

BACKGROUND: Influenza causes a great disease burden on children especially in the outpatient setting. The signs and symptoms of influenza in unselected children treated as outpatients have not been previously published.
METHODS: We assessed the clinical presentation of influenza in a prospective study of respiratory infections in preenrolled cohorts of children < or =13 years of age during 2 consecutive respiratory seasons (2231 child-seasons of follow-up). We examined the children and obtained a nasal swab for the detection of influenza during every episode of illness, regardless of the presence or absence of fever or the severity of the symptoms.
RESULTS: Influenza was virologically confirmed in 372 children, of whom 353 (95%) providing complete data on the signs and symptoms were included in the analyses. A total of 95% of these children were febrile, and 50% had fever > or =39.0 degrees C. Among children <3 years of age, 20% had fever > or =40.0 degrees C. Seventy-seven percent of the children had cough and 78% had rhinitis. In children 7 to 13 years of age, only 39% had headache and 13% had myalgia.
CONCLUSIONS: High fever is a prominent sign of influenza in children, and the clinical presentation of influenza is most severe in children <3 years of age. Headache and myalgia are not typical features of influenza in outpatient children. Most children with influenza have rhinitis during the early phase of the illness, which makes the clinical diagnosis of influenza difficult especially in the youngest children.