Introduction: The aim of this study was to describe the clinical and epidemiological features of confirmed influenza A virus infection in patients aged less than 7 years old.
Patients and methods: We performed a retrospective, descriptive study of the clinical and epidemiological features of influenza A virus infection in patients aged less than 7 years old attending three primary care centers during the 2003-2004 influenza season. Patients with influenza A infection confirmed by immunofluorescence, cell culture, or polymerase chain reaction were interviewed to obtain clinical and epidemiological data on their disease.
Results: Influenza A virus was detected in 47 patients aged between 5 months and 7 years (mean: 37.3 +/- 5.7 months). Of these, 35 children (74.4 %) were aged between 0 and 4 years. The most frequent symptoms were fever (100 %), cough (95.7 %), and rhinorrhea (76.6 %). Gastrointestinal symptoms were present in 40.4 % of the patients. The mean duration of fever was 5.2 +/- 1.8 days (range 2-8). Complications occurred in nine patients (19.2 %). The frequency of influenza-like disease in parents was 9.1 % (8/88) at diagnosis of the index case and was 23.9 % (21/88) immediately after the episode in the child (p 5 0.01). The mean number of days of absence from school was 7.5 +/- 3.6 days.
Conclusions: The mean age of our patients confirms that influenza is a frequent disease in infancy and childhood. The results demonstrate that the infection is transmitted from children to parents in the household setting, since the frequency of influenza-like symptoms in adults increases after influenza episodes in children.