Respiratory viruses circulating 2024
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Key Respiratory Viruses Circulating in 2024
During the 2023/2024 respiratory virus season, several viruses have been circulating globally, with notable regional and age-related differences. The most prominent viruses include influenza (especially A(H1N1)pdm09), respiratory syncytial virus (RSV), SARS-CoV-2 (with the JN.1 variant emerging), rhinovirus/enterovirus, and human metapneumovirus (HMPV) Mostafa2024Du2025Cunsolo2024+3 MORE.
Influenza Virus Trends and Genetic Diversity
Influenza A(H1N1)pdm09 has been the dominant strain in many regions, including Bulgaria and parts of Italy, during the 2023/2024 season, replacing A/H3N2, which was more prevalent in the previous year Cunsolo2024Korsun2025. Genetic analysis shows ongoing evolution, with several subclades and amino acid changes compared to vaccine strains, highlighting the need for continuous monitoring and vaccine updates . Influenza B (Victoria lineage) also circulated but at lower levels .
SARS-CoV-2: Variant Dynamics and Endemic Transition
SARS-CoV-2 continues to circulate, with the JN.1 variant becoming predominant in late 2023, particularly in the United States . Hospitalizations and positivity rates for COVID-19 declined in late 2024, but the virus remains a significant cause of respiratory illness, especially in older adults Mostafa2024Gratzl2024. There is evidence that SARS-CoV-2 is transitioning toward a seasonal pattern, with epidemic waves occurring alongside influenza .
Respiratory Syncytial Virus (RSV): Resurgence and Genotypes
RSV has resurged post-pandemic, especially affecting infants and young children, and is now a leading cause of pediatric hospitalizations in multiple countries, including Mexico and the US Mostafa2024Gratzl2024Leija-Martínez2024+1 MORE. RSV-A and RSV-B both circulate, with RSV-A showing slightly higher odds of hospital admission . In Mexico, several A.D lineages of RSV-A and the B.D.E.1 lineage of RSV-B have been identified, consistent with global trends .
Rhinovirus/Enterovirus and Other Respiratory Pathogens
Rhinovirus/enterovirus continues to circulate at high rates, particularly among children, and was less affected by pandemic-related interventions compared to other viruses Mostafa2024Graziani2024. Human metapneumovirus (HMPV) and parainfluenza virus have also shown increased activity in late 2024, with rising hospitalizations, especially in children Gratzl2024Leija-Martínez2024. Mycoplasma pneumoniae, adenovirus, Moraxella catarrhalis, and Haemophilus influenzae have contributed to respiratory illness, often as co-infections, increasing the complexity of clinical management .
Age-Related and Regional Patterns
- Children and Infants: RSV, rhinovirus/enterovirus, and influenza are the main causes of hospitalizations, with RSV showing a marked increase in both positivity and hospital admissions in late 2024 Mostafa2024Gratzl2024Leija-Martínez2024.
- Older Adults: SARS-CoV-2 and influenza are more commonly associated with hospitalizations in this group Mostafa2024Gratzl2024.
- Regional Differences: The dominant influenza subtype and the timing of epidemic waves vary by region, with staggered peaks for different viruses observed in China, Europe, and the Americas Du2025Cunsolo2024Korsun2025.
Shifts in Seasonality and Co-Infections
The seasonality of respiratory viruses has shifted post-pandemic, with earlier or delayed peaks and overlapping waves of different viruses Du2025Palmas2024Graziani2024. Co-infections are increasingly common, with nearly 19% of cases in Beijing involving more than one pathogen, complicating diagnosis and treatment .
Importance of Surveillance and Public Health Response
The ongoing evolution and co-circulation of multiple respiratory viruses underscore the need for robust surveillance, genomic monitoring, and flexible public health strategies. Enhanced diagnostics and vaccination campaigns are critical to managing the burden of respiratory infections, especially as SARS-CoV-2 becomes endemic and other viruses regain pre-pandemic circulation patterns Mostafa2024Du2025Korsun2025+2 MORE.
Conclusion
In 2024, the respiratory virus landscape is marked by the co-circulation of influenza (mainly A(H1N1)pdm09), RSV, SARS-CoV-2 (JN.1 variant), rhinovirus/enterovirus, and HMPV, with notable shifts in seasonality and increased co-infections. Continuous monitoring and adaptive public health measures are essential to address the evolving challenges posed by these viruses.
Sources and full results
Most relevant research papers on this topic
Genotypic Characterization of Human Respiratory Syncytial Viruses Detected in Mexico Between 2021 and 2024
HRSV-A viruses of several A.D lineages circulate globally, while HRSV-B viruses are restricted to the B.D.E.1 lineage in Mexico between 2021 and 2024.
Respiratory viruses and SARS-CoV-2 virus circulation in the provinces of Lucca and Massa Carrara during the 2022/2023 and 2023/2024 flu seasons
Effective virological diagnostics and constant monitoring of circulating viruses are crucial for correct therapy and viral circulation control in different influenza seasons.
Etiological Spectrum of Acute Respiratory Infections in Bulgaria During the 2023–2024 Season and Genetic Diversity of Circulating Influenza Viruses
Influenza A(H1N1)pdm09 is the most prevalent respiratory virus in Bulgaria, with a genetic diversity of circulating influenza viruses.
Monitoring Report: Respiratory Viruses - October 2024 Data
The overall rate of respiratory virus-associated hospitalizations decreased in October 2024, but parainfluenza and RSV hospitalizations increased, highlighting the need for close surveillance.
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Respiratory Syncytial Virus and Other Respiratory Viruses in Hospitalized Infants During the 2023–2024 Winter Season in Mexico
RSV was the most common respiratory virus in hospitalized infants during the 2023-2024 winter season in Mexico, highlighting the need for specific preventive programs to reduce morbidity and mortality.
Global analysis of respiratory viral circulation and timing of epidemics in the pre-COVID-19 and COVID-19 pandemic eras, based on data from the Global Influenza Surveillance and Response System (GISRS).
The COVID-19 pandemic altered respiratory virus circulation patterns, leading to earlier peak peaks in temperate areas in 2022 and longer epidemic durations.
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