Clinical severity and molecular typing of human rhinovirus C strains during a fall outbreak affecting hospitalized patients

BackgroundThe circulation rate and the clinical severity of infections caused by members of the new human rhinovirus C (HRV-C) species remain to be defined.ObjectivesTo investigate the epidemiologic and clinical impact of HRV-C strains in a fall outbreak interesting hospitalized patients.Study designHRV species (A–C) were determined by phylogenetic analysis following amplification of two genome regions (5′NCR and VP4/VP2) by RT-PCR. HRV species were correlated with age, respiratory tract involvement, clinical symptoms, and HRV load in respiratory secretions.ResultsDuring the first week of the period October–November 2008, single HRV infections were associated with 95% of all respiratory syndromes affecting hospitalized patients. Then, HRV infections (single + coinfections) interested about 90% of positive samples until the end of October, when they declined in frequency until reaching about 30% at the end of November. Overall, 104 HRV strains were detected and, of these, 90 could be classified by phylogenetic analysis, as follows: 45 HRV-A, 12 HRV-B, 28 HRV-C, and 5 human enterovirus D strains. HRV-C identity was confirmed by detection of cis-acting replication elements (cre) in 23/23 strains. As for severity of respiratory syndromes, unlike HRV-A and HRV-B strains, HRV-C strains were responsible for a significantly higher rate (p < 0.05) of lower respiratory tract infections in the pediatric as compared to adult patient population.ConclusionsHRV-C strains have been shown to circulate at a rate intermediate between HRV-A and HRV-B strains, showing a greater degree of clinical severity in the pediatric population.