Preplanned Studies: Respiratory Viruses andMycoplasma PneumoniaeSurveillance Among Hospitalized Children with Acute Respiratory Infections — Wuhan City, Hubei Province, China, September–November 2023

Acute respiratory infections (ARIs) are a major cause of illness and death in children under the age of five, particularly in developing countries, contributing significantly to the global burden of disease (1). The coronavirus disease 2019 (COVID-19) pandemic has changed the epidemiology of respiratory viruses andMycoplasma pneumoniae(MP) (2–3). In response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in Wuhan, China implemented a comprehensive and evolving zero-COVID policy to control the pandemic, which continued until December 2022. Since the relaxation of pandemic control measures, there has been a noticeable shift in the prevalence of respiratory viruses and MP. On November 22, 2023, the World Health Organization (WHO) reported clusters of undiagnosed pneumonia in children in China based on media and ProMED reports (4), which was later attributed to known pathogens such as the influenza virus and MP. However, the increase in ARIs and associated pathogens in Chinese children has garnered global attention (5). Therefore, this study aimed to determine the prevalence patterns of respiratory viruses and MP among children with ARIs in the Wuhan region from September 1 to November 30, 2023. Our findings demonstrate a persistent prevalence of MP and a growing trend of influenza.

We conducted a retrospective study at Wuhan Children’s Hospital, enrolling children with ARIs between September 1, 2023, and November 30, 2023. Specimens collected included nasopharyngeal aspirates/throat swabs or peripheral blood samples. These samples were analyzed using various methods such as real-time polymerase chain reaction (RT-PCR), targeted next-generation sequencing (tNGS), colloidal gold immunochromatographic tests, or direct immunofluorescence to detect microorganisms such as MP, respiratory syncytial virus (RSV), adenovirus (ADV), influenza A virus (IAV), influenza B virus (IBV), and parainfluenza virus (PIV). Demographic and clinical data were extracted from electronic medical records. Statistical analyses were performed using R (version 4.0.3, R Foundation for Statistical Computing, Minnesota, US) in RStudio (version 1.4.1103, RStudio, Inc., Minnesota, US) and GraphPad Prism (version 9.1.1.1, San Diego, CA). It is important to note that this study relied solely on the retrospective analysis of deidentified data. Ethical approval for this study was obtained from the Ethics Committee of Wuhan Children’s Hospital (No. 2023R016-E02).

From September 1, 2023, to November 30, 2023, a total of 70,016 patients sought consultation at Wuhan Children’s Hospital for ARIs, with 10,012 individuals requiring hospitalization. In the outpatient setting, 51,700 (73.8%) children provided peripheral blood samples for colloidal gold immunochromatographic tests to detect RSV, MP, and ADV. Nasopharyngeal aspirates from 8,977 (12.8%) children were tested for IAV and IBV. The average age of the children was 4.86 (3.27, 7.31) years, with the highest proportion belonging to the preschool age group (3–6 years) at 40.8%. The majority of the participants were male (56.2%). Out of the 51,700 outpatients included, 19,085 (36.9%) were infected with a single pathogen and 220 (0.4%) had co-infections. MP (36.2%) was the most commonly detected pathogen, followed by IAV (16.8%). Among the hospitalized patients, 7,568 (75.6%) children were included in the study for the simultaneous detection of MP, RSV, ADV, IAV, IBV, and PIV. Of the hospitalized children, 4,298 (56.7%) were male and 8,280 (38%) were school-age children (>6 years old), with an average age of 5.01 (3.12, 8.03) years. Across all tested settings, a total of 4,302 (56.8%) patients were infected with a single pathogen, while 373 (4.9%) were infected with multiple pathogens. Consistent with the findings in outpatients, MP (46.6%) showed the highest pathogen detection rate, followed by RSV (7.6%), PIV (5.9%), ADV (3.8%), and IAV (2.4%) (Table 1). During the study period, the enrollment of outpatients peaked during the second half of October, coinciding with an increase in MP detection. Additionally, the detection rate of MP remained consistently high throughout the study period. IAV continued to be detected, with a detection rate of approximately 10%, and peaked at the end of November (with a detection rate exceeding 30%). Furthermore, IBV started to be detected in late October but remained at low levels (Figure 1).

Figure 1.

Respiratory virus detections among enrolled children in outpatient settings. Colored lines represent the positive rate of MP and viruses over time, and the gray bar represents the number of enrolled children.

Note: Smoothed curves were generated using loess regression to enhance the visualization of trends (span=0.1).

Abbreviation: MP=Mycoplasma pneumoniae; ADV=adenovirus; IAV=influenza virus A; IBV=influenza virus B; RSV=respiratory syncytial virus.

In hospitalized patients, the detection rate of MP remains consistently high throughout the year, ranging from 30% to 60%, with the highest rates observed in October. IAV reached its peak in late November, while intermittent detections of IBV occur during this period. RSV and PIV were detected in September and October, but their numbers declined in November. ADV was consistently detected at levels below 10%. Interestingly, influenza typically peaked in late fall and winter, but the seasonal trends observed for MP and RSV in hospitalized patients differ from the expected patterns seen prior to the COVID-19 pandemic in this study (6–7) (Figure 2).

Figure 2.

Respiratory virus detections among enrolled children in inpatient settings. Colored lines represent the positive rate of MP and viruses over time, and the gray bar represents the number of enrolled children.

Note: Smoothed curves were generated using loess regression to enhance the visualization of trends (span=0.1).

Abbreviation: MP=Mycoplasma pneumoniae; ADV=adenovirus; IAV=influenza virus A; IBV=influenza virus B; RSV=respiratory syncytial virus; PIV=parainfluenza virus.