Burden of noninfluenza respiratory viral infections in adults admitted to hospital: analysis of a multiyear Canadian surveillance cohort from 2 centres

Abstract

Background: Data on the outcomes of noninfluenza respiratory virus (NIRV) infections among hospitalized adults are lacking. We aimed to study the burden, severity and outcomes of NIRV infections in this population.

Methods: We analyzed pooled patient data from 2 hospital-based respiratory virus surveillance cohorts in 2 regions of Canada during 3 consecutive seasons (2015/16, 2016/17, 2017/18; n = 2119). We included patients aged ≥ 18 years who developed influenza-like illness or pneumonia and were hospitalized for management. We included patients confirmed positive for ≥ 1 virus by multiplex polymerase chain reaction assays (respiratory syncytial virus [RSV], human rhinovirus/enterovirus (hRV), human coronavirus (hCoV), metapneumovirus, parainfluenza virus, adenovirus, influenza viruses). We compared patient characteristics, clinical severity conventional outcomes (e.g., hospital length-of stay, 30-day mortality) and ordinal outcomes (5 levels: discharged, receiving convalescent care, acute ward or intensive care unit [ICU] care and death) for patients with NIRV infections and those with influenza.

Results: Among 2119 adults who were admitted to hospital, 1156 patients (54.6%) had NIRV infections (hRV 14.9%, RSV 12.9%, hCoV 8.2%) and 963 patients (45.4%) had influenza (n = 963). Patients with NIRVs were younger (mean 66.4 [standard deviation 20.4] yr), and more commonly had immunocompromising conditions (30.3%) and delay in diagnosis (median 4.0 [interquartile range (IQR) 2.0-7.0] days). Overall, 14.6% (12.4%-19.5%) of NIRV infections were acquired in hospital. Admission to ICU (18.2%, median 6.0 [IQR 3.0-13.0] d), hospital length-of-stay (median 5.0 [IQR 2.0-10.0] d) and 30-day mortality (8.4%; RSV 9.5%, hRV 6.6%, hCoV 9.2%) and the ordinal outcomes were similar for patients with NIRV infection and those with influenza. Age > 60 years, immunocompromised state and hospital-acquired viral infection were associated with worse outcomes. The estimated median cost per acute care admission was $6000 (IQR $2000-$16 000).

Interpretation: The burden of NIRV infection is substantial in adults admitted to hospital and associated outcomes may be as severe as for influenza, suggesting a need to prioritize therapeutics and vaccines for at-risk people.

Figure 1:

Frequency distribution of influenza viruses and noninfluenza respiratory viruses (NIRVs) detected in 2119 adults admitted to hospital. Note: The frequency of all influenza viruses was 45.4%, including influenza A (H3N2), influenza A (H1N1), influenza B and untyped influenza A (not shown, 1.3%). The frequency of all NIRVs was 54.6%, including human rhinovirus/enterovirus (hRV), respiratory syncytial virus (RSV), human metapneumovirus (hMPV), human coronavirus (hCoV), parainfluenza viruses (PIV), adenovirus (AdV) or bocavirus (hBoV), and mixed viruses. The identified hCoV strains (including those in mixed infections) were: OC43 (n = 89), NL63 (n = 46), 229E (n = 30) and HKU1 (n = 21).

Figure 2:

Kaplan–Meier survival analysis in adults admitted to hospital with (A) all noninfluenza respiratory virus (NIRV) infections and (B) specific NIRV infections, compared with influenza virus (IV) infections. Note: hRV = human rhinovirus/enterovirus, RSV = respiratory syncytial virus, hCoV = human coronavirus.

Figure 3:

Ordinal outcome (clinical status) changes over 30 days since diagnosis (at baseline, day 15 and day 30) among adults inpatients with noninfluenza respiratory virus (NIRV) and influenza virus (IV) infections. Note: ICU = intensive care unit.