Influenza in children – Diagnosis, treatment and prevention

Background: The burden of influenza on children is substantial. Although mortality rates are low, the incidence of influenza is highest in children, among whom also complications are frequent. A more accurate recognition of influenza in children could enable the rational use of antiviral drugs and help to avoid unnecessary courses of antibiotics. Limited data exists on the efficacy of oseltamivir treatment and the trivalent inactivated influenza vaccine (TIV) in children. Aims and methods: We sought for signs and symptoms that could help clinicians to diagnose influenza on clinical grounds in a case-control study in children <13 years of age. We further assessed the feasibility of different diagnostics methods during the early stage of the illness in children aged 1-3 years. The efficacy of early oseltamivir treatment (started <24h from the onset of symptoms) was evaluated in a randomized controlled trial (RCT) conducted in children 1-3 years of age, and the effectiveness of TIV to prevent laboratory-confirmed influenza was determined in a prospective, observational cohort study conducted among children aged 9 months to 3 years of age. Results: Fever was the only symptom predicting influenza in children. The sensitivity of conventionally used laboratory methods to detect influenza during the first 24h of illness was 92%. The sensitivity of the influenza rapid test in the same setting was 90% for influenza A and 25% for influenza B. Early oseltamivir treatment shortened the duration of the illness in children with influenza A by 3.5-4.0 days, but no efficacy was observed against influenza B. The effectiveness of TIV was 84% against the wellmatched influenza A, while no effectiveness against the mismatched influenza B was observed. Conclusions: Laboratory diagnostics are needed for a reliable diagnosis of influenza in children and were found sensitive already during the early stage of the illness. Early oseltamivir treatment was highly effective against influenza A, but no efficacy was seen against influenza B. TIV is effective also in young children if a good match between the vaccine and circulating strain is achieved.

Burden of Influenza in Children

Background: Most children with influenza are treated as outpatients but, especially among young children, influenza-attributable illnesses often result in hospitalization. However, relatively scarce data exist on the clinical picture and the full disease burden of pediatric influenza. Prompt diagnosis of influenza could enable the institution of antiviral therapy and adequate cohorting of patients. Data are needed to help clinicians correctly suspect influenza at the time of hospital admission. Aims and methods: We conducted a prospective 2-year cohort study of respiratory infections in children aged ≤13 years to determine the incidence of influenza in outpatient children and to assess the clinical presentation of influenza in various age groups seen in primary care. We also determined the rates of different complications attributable to influenza and the absenteeism of the children and their parents due to the child’s influenza infection. We then conducted a further 16-year retrospective study of children ≤16 years of age, hospitalized with virologically confirmed influenza. We estimated the population-based rates of hospitalizations and determined the primary admission diagnoses of the hospitalized children in different age groups. Results: The average annual rate of influenza was highest (179 / 1000) among children <3 years old. In this age group, acute otitis media was diagnosed as a complication of influenza in 40% of children. High fever was the most prominent sign of influenza, and 20% of children <3 years of age had a fever ≥40oC. Most children had rhinitis already during the first days of the illness. The average annual incidence of influenzarelated hospitalization was highest (276 / 100,000) among infants <6 months of age, of whom 52% were primarily admitted due to sepsis-like illnesses. Respiratory symptoms accounted for 38% of the hospitalizations. Conclusions: Influenza causes a substantial burden of illness on outpatient children and their families. The clinical presentation of influenza is most severe in children <3 years of age. The high incidence of influenza-associated hospitalizations among infants aged <6 months calls for more effective ways to prevent influenza in this age group. The clinical manifestations of influenza vary widely in different age groups of children at the time of hospital admission. Awareness of this phenomenon is important for the early recognition of the illness and the potential initiation of effective antiviral treatment of these patients.