Subtype-specific Clinical Presentation, Medical Treatment and Family Impact of Influenza in Children 1-5 Years of Age Treated in Outpatient Practices in Germany During Three Postpandemic Years, 2013-2015.

Background: Limited data on the influenza burden in pediatric outpatients are available, especially regarding direct comparison of the cocirculating (sub)types A(H1N1)pdm09, A(H3N2) and B.
Methods: Children 1-5 years of age, unvaccinated against influenza and presenting with febrile acute respiratory infections (ARIs), were enrolled in 33 pediatric practices in Germany from 2013 to 2015 (January-May). Influenza was confirmed by multiplex polymerase chain reaction from pharyngeal swabs and (sub)typed.
Results: In 805 children with ARI, influenza was the most frequently detected respiratory virus (n = 305; 37.9%). Of 217 influenza patients included, 122 (56.2%) were infected with A(H3N2), 56 (25.8%) with A(H1N1)pdm09 and 39 (18.0%) with B. Median age was 3.7 years [interquartile range (IQR), 2.1-4.8]; 11% had underlying conditions. Median fever duration was 4 days (IQR, 3-5), and the disease duration was 9 days (IQR, 7-12). Most frequent diagnoses were pharyngitis (26%), bronchitis (18%) and acute otitis media (10%). Children received mainly antipyretics (86%) and adrenergic nasal drops/spray (53%); 9% received antibiotics and 3% oseltamivir. Thirty-six percent required at least 1 additional practice visit; 1% was hospitalized. Median absences from childcare were 5 days (IQR, 3-7); parents lost 4 workdays (IQR, 2-6). Symptoms, severity and impact on the family were largely unrelated to (sub)type. However, patients with A(H1N1)pdm09 had fewer underlying conditions (P = 0.017), whereas patients with B more often had pharyngitis (P = 0.022), acute otitis media (P = 0.012) and stenosing laryngotracheitis (P = 0.007).
Conclusions: Influenza was the most frequently detected viral pathogen in outpatient children with febrile, mostly uncomplicated ARI. In this setting, clinical manifestations and severity were similar across the (sub)types prevalent during the postpandemic seasons.