Two years after COVID-19 restrictions eased across China, the microbes behind children’s coughs and fevers have redrawn their own hierarchy. A large retrospective analysis from Ningbo, in eastern Zhejiang province, has mapped which viral and atypical bacterial pathogens dominated pediatric acute respiratory infections between January 2023 and December 2024, and the results place a bacterium, not a virus, at the top of the list. Mycoplasma pneumoniae was the single most frequently detected pathogen among more than 34,000 young patients, a finding that carries practical weight for clinicians deciding when and how to treat childhood respiratory illness in the post-pandemic era.
The study, published in BMC Infectious Diseases, drew on throat swab samples collected from 34,404 pediatric patients aged 18 years or younger who presented with respiratory symptoms at the Affiliated Women and Children’s Hospital of Ningbo University. Rather than relying on a single targeted test, the laboratory team used multiplex polymerase chain reaction, a technique that amplifies and identifies the genetic material of several pathogens simultaneously, to screen every sample for 13 common viral and atypical bacterial respiratory pathogens. Demographic details, pathogen identities and the dates on which samples were collected were then retrieved from the hospital’s laboratory database and analyzed together to reveal who was infected, with what, and when.
The headline number from the surveillance effort is an overall pathogen positivity rate of 69.14 percent, meaning that roughly seven in ten children tested carried detectable genetic evidence of at least one of the pathogens on the panel. That figure underscores how densely pathogenic material circulates among symptomatic children and illustrates the value of broad molecular panels: many of these infections would be difficult to distinguish clinically, since fever, cough and wheezing can be produced by any of a dozen different agents. Multiplex detection allows epidemiologists to see the true composition of that microbial mix rather than inferring it from symptoms alone.
Within that mix, three pathogens stood out. Mycoplasma pneumoniae, an atypical bacterium that lacks a cell wall and attaches itself to the lining of the respiratory tract, was detected in 26.94 percent of the tested children, making it the leading cause of positive findings. Human rhinovirus, the virus best known as the chief culprit behind the common cold, came second at 16.29 percent. Human adenovirus, a DNA virus capable of causing everything from pharyngitis to pneumonia, ranked third at 9.00 percent. The prominence of Mycoplasma pneumoniae is particularly notable because, as an atypical bacterium, it does not respond to the beta-lactam antibiotics often prescribed empirically for respiratory complaints, so knowing that it dominates locally can shape more rational treatment decisions.
The analysis went beyond simple prevalence counts to ask whether pathogen positivity differed across patient groups. The researchers report significant differences in positivity rates between the sexes and across age groups, indicating that the burden of specific respiratory pathogens is not distributed evenly among children. Such demographic patterns matter for clinical practice: if certain age brackets carry a disproportionately high share of detections, pediatricians can calibrate their index of suspicion, and laboratories can anticipate demand for testing among particular populations. Age-structured susceptibility is also a key input for modeling how respiratory pathogens spread through households and schools, where mixing patterns differ sharply from those of adult populations.
Seasonality, a signature feature of respiratory disease that was famously disrupted during the height of the COVID-19 pandemic, re-emerges clearly in the Ningbo data. The study documents evident seasonal variation for certain pathogens, with detection rates rising and falling across the two calendar years of surveillance. Tracking these rhythms is more than an academic exercise. Hospitals can use seasonal profiles to anticipate surges in admissions, stock appropriate diagnostics and therapeutics, and time public health messaging. The post-COVID period offers a natural experiment in how respiratory pathogen ecology rebounds when masking, distancing and reduced mixing recede, and datasets like this one provide the ground truth against which such rebound theories can be tested.
Coinfection emerged as a substantial feature of the pediatric disease landscape. Among the samples that tested positive for at least one pathogen, 19.85 percent harbored more than one, with dual infections representing the most common configuration. Coinfections complicate both biology and bedside care. On the biological side, one pathogen can damage the airway epithelium in ways that facilitate the entry or proliferation of another, potentially deepening disease severity. On the clinical side, a positive result for a common, often mild virus such as rhinovirus does not rule out a concurrent bacterial infection requiring antibiotics. Multiplex panels make such mixed infections visible, which single-pathogen testing would leave hidden.
The authors, a team spanning the hospital’s clinical laboratory, pediatrics department and a municipal key laboratory, frame the findings as an epidemiological reference for managing pediatric respiratory infections in the post-COVID-19 era. Their conclusions highlight the significant roles of Mycoplasma pneumoniae, human rhinovirus and human adenovirus in children in Ningbo and underscore the need for continued surveillance. Sustained monitoring is precisely what allows health systems to detect shifts in pathogen dominance, spot unusual out-of-season activity and respond to outbreaks before they overwhelm pediatric wards. Given that respiratory pathogens can change their circulation patterns within a single season, longitudinal datasets of this scale are among the most valuable tools available to public health authorities.
Methodologically, the study’s strengths lie in its sample size and its systematic approach. More than 34,000 specimens tested over 24 consecutive months with a standardized 13-pathogen molecular panel provide a resolution that smaller, shorter studies cannot match. The retrospective design has inherent limits, of course: it captures children who presented to one hospital with respiratory symptoms, so the findings describe a clinical population rather than the community at large, and throat swabs may vary in sensitivity across pathogens and disease stages. The researchers note that the work used non-identifiable data extracted under an ethics approval and informed consent waiver from the hospital’s institutional review board, in line with the Declaration of Helsinki.
For the wider scientific and clinical community, the Ningbo study adds a detailed post-pandemic datapoint to a growing international effort to understand how respiratory pathogen epidemiology reorganized after COVID-19. Questions remain open about whether Mycoplasma pneumoniae’s leading position reflects a genuine rebound of that bacterium after years of suppressed transmission, a shift in immunity profiles among children who grew up during the pandemic, or local factors specific to eastern China. Continued multi-season, multi-site surveillance, ideally with consistent molecular panels, will be needed to separate these explanations. In the meantime, the study offers pediatricians a clear message: in the post-COVID era, the causes of childhood respiratory infection are numerous, frequently mixed, and follow seasonal scripts that are once again worth learning by heart.
Subject of Research: Prevalence of viral and atypical bacterial respiratory pathogens in pediatric acute respiratory infections in post-COVID-19 Ningbo, China
Article Title: Prevalence of viral and atypical bacterial respiratory pathogens among pediatric patients with acute respiratory infections after COVID-19 in Ningbo, China
Article References: Zhou, C., Lu, W., Chen, Y., Hu, Q., Zhu, L., & Liu, W. (2026). Prevalence of viral and atypical bacterial respiratory pathogens among pediatric patients with acute respiratory infections after COVID-19 in Ningbo, China. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14531-9
Image Credits: AI Generated
DOI: 10.1186/s12879-026-14531-9
Keywords: Mycoplasma pneumoniae, human rhinovirus, human adenovirus, pediatric respiratory infections, multiplex PCR, coinfections, seasonal trends, COVID-19 pandemic, Ningbo China, epidemiology, BMC Infectious Diseases, surveillance
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Kristina Jarvis. (September 26, 2026). Mycoplasma Leads Pediatric Respiratory Infections in Post-COVID China, Two-Year Study Finds. Scienmag. https://scienmag.com/mycoplasma-leads-pediatric-respiratory-infections-in-post-covid-china-two-year-study-finds/
Kristina Jarvis. “Mycoplasma Leads Pediatric Respiratory Infections in Post-COVID China, Two-Year Study Finds.” Scienmag, 26 September 2026, https://scienmag.com/mycoplasma-leads-pediatric-respiratory-infections-in-post-covid-china-two-year-study-finds/. Accessed 26 September 2026.
Kristina Jarvis. “Mycoplasma Leads Pediatric Respiratory Infections in Post-COVID China, Two-Year Study Finds.” Scienmag. September 26, 2026. https://scienmag.com/mycoplasma-leads-pediatric-respiratory-infections-in-post-covid-china-two-year-study-finds/
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Tags: atypical bacterial pathogensBMC Infectious Diseaseschildhood cough and fever causescoinfectionsCOVID-19 pandemicepidemiologyhuman adenovirushuman rhinovirusmultiplex PCRmultiplex PCR pathogen detectionMycoplasma pneumoniaeNingbo ChinaNingbo hospital respiratory studypediatric infectious disease trendspediatric respiratory infectionspost-COVID Chinapost-pandemic respiratory infection hierarchyrespiratory illness in childrenretrospective infection studyseasonal trendssurveillanceviral vs bacterial dominance
