SynthesisEpidemiology (Cambridge, Mass.)2015
Review Article: The Fraction of Influenza Virus Infections That Are Asymptomatic: A Systematic Review and Meta-analysis.
Synthesis in Epidemiology (Cambridge, Mass.), 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 100 papers, 4 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
100 citing papers in PubMed, 4 syntheses or guidelines pooled it, 161 citations in OpenAlex.
- Using secondary cases to characterize the severity of an emerging or re-emerging infection.Nature communications · 2021Pooled it
- Spotlight influenza: Laboratory-confirmed seasonal influenza in people with acute respiratory illness: a literature review and meta-analysis, WHO European Region, 2004 to 2017.Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin · 2021Pooled it
- Asymptomatic SARS-CoV-2 infection: A systematic review and meta-analysis.Proceedings of the National Academy of Sciences of the United States of America · 2021Pooled it
- Assessment and management of asymptomatic COVID-19 infection: A systematic review.Travel medicine and infectious diseasePooled it
- Clinical and public health economic impact of rapid strain-matched vaccination in influenza pandemic mitigation: A UK-like population dynamic transmission model.Human vaccines & immunotherapeutics · 2026Article
- Live Attenuated Influenza Vaccine (LAIV) for Children for the Prevention of Influenza Illness in Sweden: A Cost-Effectiveness Analysis.Infectious diseases and therapy · 2026Article
- Estimating the Range and Duration of Post-influenza Symptoms, Conditions, and Diseases.Open forum infectious diseases · 2026Article
- Multi-source agent-based modeling to optimize influenza mitigation strategies in Hong Kong.Nature communications · 2026Article
- Dermcidin has antiviral activity and protects against influenza.Proceedings of the National Academy of Sciences of the United States of America · 2026Article
- Avian Influenza H5N1 Infection During Pregnancy: Preparing for the Next Flu Pandemic and Improving Perinatal Outcomes.Viruses · 2026Review
- Asymptomatic and Mildly Symptomatic Influenza Virus Infections by Season: Case-Ascertained Household Transmission Studies, United States, 2017-2023.The Journal of infectious diseases · 2025Article
- Long-Term Sewage Survey of SARS-CoV-2, Influenza A and Respiratory Syncytial Virus (RSV), and Correlation to Human Cases in a City with One Million Inhabitants.Microorganisms · 2025Article
- Influenza Vaccine Effectiveness Against Illness and Asymptomatic Infection in 2022-2023: A Prospective Cohort Study.Clinical infectious diseases : an official publication of the Infectious Diseases Society of America · 2025Article
- A Potential Platform for Future Vaccine Trials Identifies a High Incidence of Symptomatic and Asymptomatic Influenza Infection Among Children Aged 6 to 23 Months in South Africa.The Journal of infectious diseases · 2025Article
- Estimated Effectiveness of Influenza Vaccines in Preventing Secondary Infections in Households.JAMA network open · 2024Article
- Avian influenza in birds: Insights from a comprehensive review.Veterinary world · 2024Review
- Reconstructed influenza A/H3N2 infection histories reveal variation in incidence and antibody dynamics over the life course.PLoS biology · 2024Article
- Occupational exposure monitoring of airborne respiratory viruses in outpatient medical clinics.Aerosol science and technology : the journal of the American Association for Aerosol Research · 2024Article
- Epidemiological characteristics of influenza outbreaks in schools in Jiangsu Province, China, 2020-2023 post-COVID-19 pandemic.BMC infectious diseases · 2024Article
- Influenza virus shedding and symptoms: Dynamics and implications from a multiseason household transmission study.PNAS nexus · 2024Article
40 more citing papers are in PubMed but not listed here.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
4 authors at 1 institution in 3 countries.
Funding
Abstract
backgroundThe fraction of persons with influenza virus infection, who do not report any signs or symptoms throughout the course of infection is referred to as the asymptomatic fraction.
methodsWe conducted a systematic review and meta-analysis of published estimates of the asymptomatic fraction of influenza virus infections. We found that estimates of the asymptomatic fraction were reported from two different types of studies: first, outbreak investigations with short-term follow-up of potentially exposed persons and virologic confirmation of infections; second, studies conducted across epidemics typically evaluating rates of acute respiratory illness among persons with serologic evidence of infection, in some cases adjusting for background rates of illness from other causes.
resultsMost point estimates from studies of outbreak investigations fell in the range 4%-28% with low heterogeneity (I = 0%) with a pooled mean of 16% (95% confidence interval = 13%, 19%). Estimates from the studies conducted across epidemics without adjustment were very heterogeneous (point estimates 0%-100%; I = 97%), while estimates from studies that adjusted for background illnesses were more consistent with point estimates in the range 65%-85% and moderate heterogeneity (I = 58%). Variation in estimates could be partially explained by differences in study design and analysis, and inclusion of mild symptomatic illnesses as asymptomatic in some studies.
conclusionsEstimates of the asymptomatic fraction are affected by the study design, and the definitions of infection and symptomatic illness. Considerable differences between the asymptomatic fraction of infections confirmed by virologic versus serologic testing may indicate fundamental differences in the interpretation of these two indicators.
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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.