Background: The aim of this study was to determine the burden of influenza-related diseases in children 0 to 11 months of age during the peak of the 2001 to 2002 influenza epidemic.
Methods: This was a prospective study at the Pediatric Emergency Department of Edouard Herriot tertiary teaching hospital in Lyon, France. The study included 304 infants 0 to 11 months of age. Consecutive patients were systematically enrolled during the 4 weeks of the influenza epidemic peak (Weeks 3 to 6, 2002). Influenza viruses were detected by antigen detection and virus culture from nasal swabs. Structured telephone interviews were conducted on Days 8 and 15 after virus detection. There was also a 6-month survey into the medicoadministrative database to detect late complications that required delayed hospitalization of influenza-positive children.
Results: Influenza virus was detected in 99 (33%) of 304 patients (A/H3N2 in 30% and B in 3%). Nonrespiratory symptoms were the dominant clinical manifestations in 30% of influenza-positive children. One child with influenza presented with febrile seizures. Twenty (20%) children with influenza were hospitalized. Parents reported recovery from the illness in 63 and 94% of children on Days 8 and 15, respectively. The median length of an influenza episode was 8 days.
Conclusions: Our results confirm the high prevalence of influenza-related morbidity in infants during the epidemic peak. One child in three consulting to the pediatric emergency room had a virologically confirmed influenza infection regardless of the body temperature. Every fifth child with influenza was admitted to hospital, which corresponds to an admission rate of 237 per 100 000 children 0 to 11 months of age.