Human Bocavirus Often Travels With Other Viruses, Global Analysis Finds

Human bocavirus, a small DNA virus first discovered two decades ago, has long been recognized as a common inhabitant of the respiratory tract in young children, yet its true epidemiological profile has remained stubbornly difficult to pin down. A new systematic review and meta-analysis published in BMC Infectious Diseases brings together data from across five continents to map how frequently the virus appears, when it strikes through the year, and how often it shares airways with other pathogens. The findings, compiled by a team of researchers based in China, suggest that coinfection is the rule rather than the exception for this elusive virus.

The research team, led by Shi Dong and Haokun Mei of Nanjing Medical University alongside colleagues at several Chinese institutions, conducted a comprehensive search of PubMed and Web of Science that initially returned 301 studies. After rigorous screening according to pre-specified design criteria, 21 studies met eligibility requirements, encompassing 74,424 participants and 4,274 human bocavirus positive patients drawn from nine countries across five continents. The analysis was registered prospectively on PROSPERO under registration number CRD420261460519, and the review followed established PRISMA reporting guidelines with quality assessment using the Joanna Briggs Institute framework.

For the primary prevalence estimate, the authors applied strict inclusion rules: only cross-sectional or consecutive surveillance studies with a valid denominator were admitted, and studies that exclusively enrolled patients already known to be bocavirus positive were excluded to avoid inflating prevalence. Eighteen studies survived these filters. The pooled global prevalence of human bocavirus among patients tested, most of them presenting with respiratory tract infections, was 9.7 percent, with a 95 percent confidence interval spanning 6.4 to 13.1 percent. Notably, the 95 percent prediction interval stretched from 0.0 to 25.1 percent, an unusually wide range that signals profound heterogeneity across settings, populations, and study designs.

That heterogeneity is not merely a statistical nuisance; it is a central biological finding. The authors report that human bocavirus prevalence, seasonality, and coinfection patterns are significantly shaped by geographic region, age, and socioeconomic factors. Viral detection rates in a densely populated urban pediatric ward in East Asia may bear little resemblance to those in a European outpatient clinic, and the meta-analysis makes clear that any single-country estimate should be extrapolated with caution. The wide prediction intervals serve as a quantitative reminder that the virus’s behavior is embedded in local epidemiological contexts rather than governed by a single global pattern.

Seasonality emerged as one of the more intriguing dimensions of the analysis. Twelve studies initially contributed data on the timing of infections. The crude proportion of bocavirus positive cases occurring in summer was 17.2 percent, but after the authors excluded three statistical outliers, identified by pre-specified criteria of studentized residuals greater than 2.0 and a reduction in heterogeneity exceeding 20 percentage points, the adjusted summer proportion rose to 23.2 percent with a confidence interval of 17.2 to 29.1 percent. No outliers were detected for spring, autumn, or winter, suggesting that while the virus circulates year round, a meaningful fraction of its burden falls in the warmest months, a pattern that distinguishes it from strictly winter-peaked pathogens such as respiratory syncytial virus or influenza.

The COVID-19 pandemic left a detectable fingerprint on these seasonal rhythms. The analysis found that the seasonal peak of human bocavirus activity was delayed by 1.6 months after the pandemic, and the phase distribution of infections became more concentrated in the post-pandemic era. This observation aligns with broader reports of disrupted respiratory virus ecology following the widespread deployment of non-pharmaceutical interventions, which temporarily suppressed transmission of many common respiratory pathogens and subsequently reshaped the timing and intensity of their return. The authors note that the higher coinfection proportion observed in the post-pandemic subgroup was not, however, a statistically significant moderator effect, with meta-regression yielding a p value of 0.721.

The most clinically consequential finding concerns coinfection. Across 18 studies, the overall proportion of human bocavirus infections that involved at least one additional pathogen was 65.9 percent, with a confidence interval of 64.3 to 67.5 percent. Among specific co-pathogens, respiratory syncytial virus showed the highest coinfection rate, followed by other common respiratory viruses including human rhinovirus, adenovirus, human metapneumovirus, parainfluenza virus, influenza virus, and enterovirus. In other words, when clinicians detect bocavirus in a pediatric respiratory sample, roughly two-thirds of the time another virus is present as well, complicating any straightforward attribution of disease to a single agent.

Does coinfection matter for outcomes? The meta-analysis suggests it does. Patients with coinfections had a significantly higher risk of pneumonia than those with bocavirus monoinfections, with an odds ratio of 1.53 and a confidence interval of 1.08 to 2.18. Coinfection was also associated with an average of 0.80 additional days of hospital stay. These numbers, while statistically significant, come with important caveats that the authors themselves emphasize. The clinical analyses rested on only nine studies, the majority of which originated from China, and bacterial co-pathogens were not assessed at all. Because bacterial pneumonia is a frequent and serious complication of viral respiratory infections, its absence from the pathogen panel means the full clinical impact of mixed infections is likely underestimated.

The methodological transparency of the review deserves attention in its own right. By pre-specifying outlier exclusion criteria before running analyses, reporting both crude and adjusted estimates, and presenting prediction intervals alongside confidence intervals, the authors offer a model of cautious inference in a field where pooled estimates are often presented with more certainty than the underlying data warrant. The confidence intervals describe the precision of the average effect across studies, while prediction intervals describe the plausible range a new study might observe, and the gulf between the two in this analysis is a candid acknowledgment of how much local variation remains.

Looking forward, the authors call for research incorporating standardized protocols and comprehensive pathogen testing, including bacterial diagnostics and quantitative viral load measurements, to clarify the clinical impact of human bocavirus coinfections. Whether the virus acts as a primary pathogen, a passenger amplified by concurrent illness, or a cofactor that worsens disease driven by other agents remains one of the central unanswered questions in respiratory virology. As molecular multiplex panels become standard in clinical settings worldwide, the data needed to answer that question are accumulating rapidly, and syntheses like this one provide the essential baseline against which future studies can be measured.

Subject of Research: Global epidemiology, seasonality, and clinical impact of human bocavirus coinfections in respiratory tract infections

Article Title: Epidemiology and clinical patterns of human bocavirus coinfections: a systematic review and meta-analysis

Article References: Dong, S., Mei, H., Tan, B., Ren, H., Xu, Y., Yang, D., Dai, Q., Ji, M., & Dai, G. (2026). Epidemiology and clinical patterns of human bocavirus coinfections: a systematic review and meta-analysis. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14478-x

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14478-x

Keywords: human bocavirus, coinfection, respiratory syncytial virus, pneumonia, systematic review, meta-analysis, epidemiology, seasonality, pediatric respiratory infections, viral epidemiology, BMC Infectious Diseases, COVID-19 pandemic