The purpose of this study is to investigate the effect of cohort isolation of RS(respiratory syncytial virus)-positive bronchiolitis versus RS-negative bronchiolitis on prevention of co-infection and clinical disease severity. Furthermore the investigators want to elucidate general epidemiological data on bronchiolitis concerning viral causes and the associated clinical severity.

The investigators want to conduct a prospective cohort study, comparing incidence of co-infection and clinical severity, in two cohort: one with isolation of RS positive bronchiolitis as a separate cohort within bronchiolitis and one without isolation (all children with RS-negative bronchiolitis are nursed together independent of viral agent)

Acute bronchiolitis is a major cause for hospitalisation in young children during the winter season. Human Respiratory Syncytial Virus (RSV) is the most frequently identified virus, however with the use of new and highly sensitive molecular amplification methods, the role of other viral pathogens in bronchiolitis has been increasingly recognized. Various disease severity has been shown for a range of respiratory viruses, and double viral infection is relatively common, occurring in about 10-30% of hospitalised patients. There is no consensus, however, on the impact of such co-infection on disease severity: Some studies showed more severe disease in co-infected children,while others did not.Most hospitals perform routine viral testing to identify and isolate RSV-infected infants, with the aim of reducing the risk of nosocomial cross-infection of other patients.However, no good evidence is available of how effective this approach is in preventing nosocomial cross-infections among admitted patients with the clinical diagnosis of bronchiolitis.

Because of limited isolation facilities, patients with bronchiolitis admitted to our pediatric ward initially share a room, pending the results of virological diagnosis. We hypothesize that contact isolation measures and maintaining enough distance between the beds in a shared room should be sufficient in preventing cross-infection, since the major route of transmission of respiratory viruses is by close contact with infected secretions and not by small-particle aerosol.

Objectives The purpose of this study was to determine the incidence of cross-infection in children hospitalised for bronchiolitis, when patients with RSV share the same room with patients with bronchiolitis infected with another virus during the first day of admission.

Study design The study was conducted at our 30-bed pediatric ward. From December 2011 through March 2012, all eligible infants younger than two years of age hospitalised for acute bronchiolitis were prospectively enrolled. Bronchiolitis was defined as acute respiratory disease, accompanied by coryza, cough, inspiratory crackles and/or expiratory wheezing on auscultation. Infants with chronic lung disease, congenital heart disease and Down's syndrome were excluded.

We prospectively collected the following demographic and clinical information, including presence and number of room mates, virological diagnosis of the patient and room mates, and daily dyspnoea score assessed by an independent researcher, who was unaware of virological diagnosis. A nasopharyngeal aspirate was collected for virological diagnosis by direct immunochromatographic antigen detection immediately at admission, every fourth day during admission, and five to seven days after discharge.All patients with bronchiolitis were treated with standard hygienic measures. Medical and nursing personnel wore gowns, gloves and masks during patient contact and washed their hands before and after patient contact. Parents and visitors were asked to wash hands before leaving the room. On the first day of admission, pending the results of the RSV-PCR (polymerase chain reaction), patients shared a two- or four-bed room, with beds separated at least 1,5 meter. Cohorting of RSV-infected patients commenced as soon as the result of RSV-PCR was known, generally within one day after admission.

Statistical analysis Chi-square test was used to compare categorical data, Mann-Whitney U-tests for continuous data because of skewed distributions. Statistical analyses were performed using Statistical Package for the Social Sciences (SPSS) version 19.

Inclusion Criteria:

• patients under 2 years of age
• hospitalized for bronchiolitis

Exclusion Criteria:

• bronchopulmonary disease
• congenital heart defect,
• congenital pulmonary disease,
• Down's syndrome

Infants admittted for bronchiolitis under 2 years of age