Highly frequent infections with human rhinovirus in healthy young children: a longitudinal cohort study.

van der Zalm, Marieke M; Wilbrink, Berry; van Ewijk, Bart E; Overduin, Pieter; Wolfs, Tom F W; van der Ent, Cornelis K

BACKGROUND Human rhinoviruses (HRVs) are an important cause of respiratory tract infections. OBJECTIVES We questioned whether the high prevalence rates of HRVs found in epidemiological studies is due to long-term individual continuity or a result of frequent infections with different HRV subtypes. STUDY DESIGN In a 6-month winter period 18 healthy controls, aged 0-7 years, were at least sampled every two weeks for HRV-PCR, irrespective of respiratory symptoms. All HRV positive samples were genotyped to determine HRV diversity. RESULTS In total 272 samples were collected. HRV was found in 101/272 (37%) samples. Genotyping revealed 27 different HRV subtypes. A median of 3.0 different HRV subtypes was found per child. Re-infections and continuity with identical HRV sequences were observed. The number of HRVs were higher in the youngest age group (p=0.01) and they had more different HRV subtypes (p=0.05) compared to oldest age group. CONCLUSIONS We found a high HRV exposition with a considerable diverse population of HRV subtypes in young children. These results have major implications for future research into the pathogenic role of HRV in respiratory diseases. Characterisation of subtypes will be necessary to discriminate between prolonged continuity and re-infections in patients with respiratory diseases.