Monitoring Report: Respiratory Viruses - September 2024 Data
Authors: Gratzl Samuel , Cartwright Brianna M Goodwin , Rodriguez Patricia J , Baker Charlotte , Do Duy , Stucky Nicholas L 
Published: January 2024

Background

Few sources regularly monitor hospitalizations associated with respiratory viruses. This study provides current hospitalization trends associated with six common respiratory viruses: COVID-19, influenza, human metapneumovirus (HMPV), parainfluenza virus, respiratory syncytial virus (RSV), and rhinovirus.

Objective

This study aims to supplement the surveillance data provided by the CDC by describing latest trends (through October 13, 2024) overall and for each respiratory virus. This study also provides valuable insight into two at-risk populations: infants and children (age 0-4) and older adults (age 65 and over).

Methods

Using a subset of real-world electronic health record (EHR) data from Truveta, a growing collective of health systems that provides more than 18% of all daily clinical care in the US, we identified people who were hospitalized between October 01, 2019 and October 13, 2024. We identified people who tested positive for any of the six respiratory viruses within 14 days of the hospitalization. We report weekly trends in the rate of hospitalizations associated with each virus per all hospitalizations for the overall population and the two high-risk sub populations: infants and children and older adults.

Results

We included 748,659 hospitalizations of 692,435 unique patients who tested positive for a respiratory virus between October 01, 2019 and October 13, 2024.

Overall, the rate of hospitalizations associated with respiratory viruses decreased throughout September 2024; there was a 27.9% reduction in the rate of hospitalizations from the first week of September to the first week of October. COVID-associated hospitalizations saw a notable decline of 46.1%, while influenza-associated hospitalizations remained stable. In contrast, there were increases in hospitalizations for parainfluenza virus (+132.6%), RSV (+149.9%), and rhinovirus (+22.8%). In the first week of October 2024, respiratory virus-associated hospitalizations accounted for 2.0% of all hospitalizations. Overall, test positivity rates also decreased, with an overall drop of 39.3%, particularly in COVID positivity (-53.7%). However, rhinovirus test positivity increased slightly to 21.0%, reflecting a 4.5% rise.

Discussion

The data indicates a continued decline in respiratory virus-associated hospitalizations across the overall population, particularly for COVID-19. The notable increases in parainfluenza and RSV hospitalizations suggest a shift in the respiratory virus landscape, highlighting the need for ongoing surveillance. The decrease in test positivity rates for COVID-19 is encouraging, but the rising trend in rhinovirus positivity warrants attention as it may indicate a growing prevalence of this virus.

Trends in surveillance

Overall population

For the overall population, the rate of hospitalizations associated with respiratory viruses decreased by 27.9% in the first week of October 2024 compared to September 2024. The decline in COVID-associated hospitalizations (-46.1%) was substantial, while influenza-associated hospitalizations remained unchanged. Notably, parainfluenza and RSV-associated hospitalizations saw substantial increases of 132.6% and 149.9%, respectively, alongside a smaller increase in rhinovirus-associated hospitalizations (+22.8%). In the first week of October, respiratory virus-associated hospitalizations accounted for 2.0% of all hospitalizations.

The overall rate of positive tests decreased by 39.3%, with COVID test positivity dropping substantially (-53.7%). However, rhinovirus test positivity increased slightly to 21.0%, indicating a potential rise in this virus’s prevalence.

Infants and children (age 0-4)

In the population aged 0-4 years, respiratory virus-associated hospitalizations increased slightly by 2.9% throughout September 2024. COVID-associated hospitalizations decreased by 14.3%, while parainfluenza-associated hospitalizations rose drastically (+242.9%) and RSV-associated hospitalizations increased by 177.6%. In the first week of October, 2.8% of all hospitalizations in this age group were associated with a respiratory virus, with rhinovirus being the largest contributor at 2.1%.

The overall test positivity rate decreased by 8.6%, with COVID test positivity dropping substantially (-53.5%). Rhinovirus test positivity remained high at 50.4%, although it decreased by 7.4% compared to September.

Older adults (age 65 and over)

Among older adults (age 65 and over), there was a decrease of 34.0% in hospitalizations associated with respiratory viruses throughout September 2024. COVID-associated hospitalizations decreased by 46.4%, while influenza-associated hospitalizations remained stable. In the first week of October, respiratory virus-associated hospitalizations accounted for 2.4% of all hospitalizations in this age group, with rhinovirus being a notable contributor at 0.6%.

The overall rate of positive tests decreased by 41.6%, with COVID test positivity dropping substantially (-46.3%). Rhinovirus test positivity increased to 8.9%, reflecting a 23.7% rise, which may indicate a growing concern for this virus among older adults.