Respiratory Viruses Show Distinct Hospital Admission Patterns

RESPIRATORY viruses showed distinct links to pneumonia, bronchiolitis, and airway exacerbations, while collectively tracking hospital admissions.

A study of 1,801 hospital admissions for acute respiratory infections found that influenza A, respiratory syncytial virus (RSV), and human rhinovirus (HRV) showed different associations with major respiratory presentations. However, overall respiratory virus circulation showed the strongest temporal relationship with hospital admission patterns.

Respiratory Viruses Show Different Clinical Patterns

Researchers analyzed admissions between November 2019 and March 2020, before the emergence of severe acute respiratory syndrome coronavirus 2. Patients were classified as having pneumonia, bronchiolitis, or reactive airway exacerbations, while respiratory samples were tested for influenza A and other common respiratory viruses.

Influenza A was most strongly represented among patients admitted with pneumonia. Of patients with influenza A alone, 76.5% were in the pneumonia group. The influenza A wave peaked during epidemiological week 5 of 2020, when it accounted for 33% of infections tested.

Other respiratory viruses were more prominent in bronchiolitis and reactive airway exacerbations. RSV was the main virus associated with bronchiolitis, particularly among infants, while HRV was the most common viral trigger identified in acute exacerbations of asthma or chronic obstructive pulmonary disease (COPD).

Infants younger than 1 year accounted for more than 90% of bronchiolitis admissions associated with influenza A testing, and age emerged as one of the strongest determinants of clinical presentation.

Combined Viral Activity Tracks Hospital Admissions

Although individual respiratory viruses showed preferential associations with particular conditions, no virus was confined to a single presentation. Viral co-infections were also uncommon.

When researchers combined activity from all respiratory viruses, viral circulation was strongly correlated with hospital admissions, with a correlation coefficient of 0.88. This relationship was stronger than patterns observed for individual pathogens, suggesting that the collective burden of circulating respiratory viruses may better reflect seasonal demand on hospital services.

Air quality measures, including ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, nitrogen oxide, and fine particulate matter, did not show consistent independent associations with acute respiratory infection admissions after full adjustment.

The researchers noted that the relatively short five month study period and weekly averaging of air quality measurements limited interpretation of environmental effects. Potential diagnostic overlap between bronchiolitis and viral pneumonia in young children was another limitation.

Overall, the findings suggest that age and viral type help shape acute respiratory presentations, while combined respiratory virus circulation may provide a broader indication of seasonal hospital burden.

Reference
Husein M et al. Influenza A and other respiratory viruses show distinct associations with acute respiratory presentations and temporal correlation with hospital admissions. J Med Microbiol. 2026;75(9):002203.

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