Characterization of 2009 H1N1 pandemic influenza in a population of Dutch children with influenza‐like signs and symptoms

Smit, Patrick M; Bongers, Karlien M; Kuiper, Rosalie JL; von Rosenstiel, Ines A; Smits, Paul HM; Brandjes, Dees PM

Aim: To determine causative respiratory pathogens and describe epidemiological and clinical characteristics in a paediatric population with influenza‐like illness during the 2009 H1N1‐pandemic. Methods: Observational study of 412 children visiting an outpatient clinic of a Dutch teaching hospital. Results: From August to December 2009, 412 children were tested at the clinic; 32% proved H1N1‐positive, confirmed by reverse‐transcriptase‐polymerase‐chain‐reaction (RT‐PCR). Pathogens were detected in 65% of samples. Influenza A(H1N1) (n = 132), human rhinovirus (n = 55), respiratory syncytial virus (n = 45) and adenovirus (n = 34) were mostly identified. Co‐infections were seen in 34 children (8.3%). Mean age was 6.8 and 4.2 years in H1N1‐positive and H1N1‐negative cases, respectively (p < 0.01). H1N1‐positive outpatient children reported fever, cough and rhinorrhoea more frequently than their H1N1‐negative counterparts. Of 72 hospitalized children, 31% proved H1N1‐positive; all showed a relatively mild clinical illness. None of the children had been admitted to an intensive care unit or died. Oseltamivir treatment was initiated in 72 children and discontinued in 42 (63%) when RT‐PCR results turned negative. Conclusion: The 2009 H1N1‐pandemic showed a mild clinical course in a Dutch paediatric outpatient clinic population. Respiratory pathogens were detected in the majority of children with influenza‐like illness and influenza A(H1N1) virus was identified in one‐third. Testing symptomatic children during an influenza pandemic has effectively limited the use of oseltamivir.