Introduction
Respiratory viruses pose a significant threat to global health, causing illnesses ranging from minor colds to severe conditions like pneumonia and acute respiratory distress syndrome (ARDS). They are particularly virulent in children, leading to high rates of pneumonia in infants and young children. Before the COVID-19 outbreak, research focused on viruses like influenza and respiratory syncytial virus (RSV), emphasizing vaccine development and antiviral therapies.
Recent studies have examined changes in viral epidemiology during the pandemic, highlighting the effects of public health measures such as lockdowns and mask mandates. However, there is a scarcity of detailed analyses focusing on the epidemiological trends of common respiratory viruses across different phases: pre-control, during the pandemic, and post-control.
This study presents a seven-year analysis of common respiratory viruses among children at a tertiary hospital in Fuzhou, China, from January 2017 to December 2023, examining the impact of pandemic control measures. The research aims to provide insights into future protective strategies.
Methods
Study Design
A retrospective study was conducted at a hospital in Fuzhou with a broad patient base, representing pediatric care in the region. Over a seven-year period, 24,838 children with respiratory infections were admitted.
Phases of the Study
- Phase I (Pre-control): January 1, 2017, to December 31, 2019.
- Phase II (Control): January 1, 2020, to December 31, 2022.
- Phase III (Post-control): January 1, 2023, to December 31, 2023.
Inclusion and Exclusion Criteria
Inclusion:
- Children aged below 14 years.
- Acute infection symptoms (fever, cough, abnormal breath sounds, etc.).
Exclusion:
- Non-infectious diseases (e.g., allergic diseases, tumors).
- Congenital respiratory dysplasia or impaired immune systems.
- Incomplete medical records.
Sample Collection and Detection
Trained medical staff collected throat swabs using flocked swabs, which were stored in a viral transport medium and tested using the Respiratory Virus Antigen Detection Kit (Genesis) to identify common viruses like RSV, ADV, Flu A, Flu B, PIV-1, PIV-2, and PIV-3.
Statistical Analysis
All analyses were performed using SPSS Statistics version 27.0. Descriptive statistics were calculated and comparisons among groups were made using Chi-square or Fisher’s exact tests where appropriate.
Results
Overall Detection Rate
Out of 24,838 cases, 4439 tested positive for respiratory viruses, resulting in an overall detection rate of 17.87%. RSV had the highest detection rate at 11.45%, followed by PIV-3 (1.96%), Flu A (1.55%), ADV (1.31%), and PIV-1 (0.76%). Flu B (0.44%) and PIV-2 (0.39%) had lower rates.
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Figure 1 Overall respiratory virus detection rate among hospitalized children (%). Abbreviations: ADV, adenovirus virus; Flu A, influenza A virus; Flu B, influenza B virus; PIV-1, parainfluenza virus types 1; PIV-2, parainfluenza virus types 2; PIV-3, parainfluenza virus types 3; RSV, respiratory syncytial virus. |
Comparison Across Three Phases
The detection rates of respiratory viruses varied significantly across the three phases. Post-control phase showed lower detection rates compared to pre and during-control phases, particularly for severe viruses like RSV.
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Table 2 Comparison of Detection Rates of Respiratory Viruses in Three Phases |
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Figure 2 Comparison of detection rates of respiratory viruses in three phases (%). Abbreviations: ADV, adenovirus virus; Flu A, influenza A virus; Flu B, influenza B virus; PIV-1, parainfluenza virus types 1; PIV-2, parainfluenza virus types 2; PIV-3, parainfluenza virus types 3; RSV, respiratory syncytial virus. |
Detection Rates by Age and Gender
The highest detection rate was among children under one year old, comprising 50.86% of positive cases. RSV was predominantly detected in infants and young children. Flu A prevalence increased with age, peaking in children over nine years old.
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Table 3 Comparison of Pathogen Infection by Gender and Age |
Monthly Distribution of Respiratory Viruses
The monthly prevalence of respiratory viruses varied significantly. RSV and PIV-3 showed seasonal patterns, with RSV peaking in winter and early spring, and PIV-3 showing a seasonal shift post-pandemic.
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Figure 3 Monthly distribution of respiratory viruses (%). Abbreviations: ADV, adenovirus virus; Flu A, influenza A virus; Flu B, influenza B virus; PIV-1, parainfluenza virus types 1; PIV-2, parainfluenza virus types 2; PIV-3, parainfluenza virus types 3; RSV, respiratory syncytial virus. |
Mixed Infections
Mixed infections were rare, with 0.40% (100 cases) of the total, predominantly involving PIV-3 with RSV. This trend was most pronounced in the pre-control phase, suggesting a shift in viral dynamics during the pandemic phase.
Discussion
The study highlights significant changes in respiratory virus detection rates following the relaxation of COVID-19 control measures. This indicates that while NPIs have effectively reduced viral spread, some viruses like RSV and PIV-3 continued to circulate.
RSV and PIV-3 exhibited altered seasonality patterns, moving from spring and summer to autumn and winter during the pandemic and reverting to their usual seasonal cycles after. This suggests that hospital admissions and severe cases represent a biased sample, and community-level data could provide a more comprehensive picture.
The study has several limitations, including a relatively small sample size for the post-control phase and a focus on only seven common respiratory viruses. Future research should include other prevalent viruses and consider severe cases to better understand the dynamics of respiratory infections.
Conclusion
COVID-19 control measures have significantly reduced the spread of respiratory viruses among children. However, RSV and PIV-3 remained prevalent and were influenced by seasonal variations. Continued surveillance and targeted interventions, especially for RSV and Flu A, are essential to reduce respiratory infections in