The impact of COVID-19 pandemic on influenza surveillance: a systematic review and meta-analysis

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Abstract

Background

Influenza activity was reported to be below the seasonal levels during the COVID-19 pandemic globally. However, during the SARS-CoV-2 outbreak, the routine real-time surveillance of influenza like illness (ILI) and acute respiratory infection (ARI) was adversely affected due to the changes in priorities, economic constraints, repurposing of hospitals for COVID care and closure of outpatient services.

Methods

A systematic review and meta-analysis were carried out to assess the pooled proportion of symptomatic cases tested for influenza virus before the current pandemic in 2019 and during the pandemic in 2020/21. An electronic search of PubMed/MEDLINE, Scopus and Google Scholar was carried out for the articles reporting the impact of the COVID-19 pandemic on Influenza surveillance among humans using search terms. The study was designed based on PRISMA guidelines and the meta-analysis was performed to synthesise the pooled proportion of patients sampled for influenza with 95% confidence interval (CI).

Results

The nine qualified studies from the WHO-European region, Canada, Japan, Germany, Italy, Spain, South Africa and the United States were pooled by random-effects meta-analysis. The overall pooled proportion of symptomatic cases sampled for influenza surveillance before and during the pandemic was 2.38% (95% CI 2.08%-2.67%) and 4.18% (95% CI 3.8%-4.52%) respectively. However, the pooled proportion of samples tested for influenza before the pandemic was 0.69% (95% CI 0.45-0.92%) and during the pandemic was 0.48% (95% CI 0.28-0.68%) when studies from Canada were excluded.

Conclusion

The meta-analysis concludes that globally there was a decline in influenza surveillance during the COVID-19 pandemic except in Canada.

Key Messages

  • The nine observational studies from Europe, Canada, Japan, South Africa and the United States were qualified for the meta-analysis

  • A steep decline in the seasonal influenza activity in both northern and southern hemispheres was observed

  • Almost double the number of symptomatic cases were sampled as part of influenza surveillance during the current pandemic in Canada

  • Except in Canada, a decline in influenza surveillance globally during the COVID-19 pandemic was observed

Article activity feed

  1. SciScore for 10.1101/2022.03.31.22273236: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    SARI: A case is defined as SARI if the symptoms begin within the past ten days with fever (measured≥ 38□) and respiratory infection (cough) necessitating hospitalization9. 2 Study Protocol: An electronic search of PubMed/MEDLINE, Scopus and Google Scholar was carried out for all the articles published between January 2020 and December 2021 concerning the impact of the COVID-19 pandemic on Influenza surveillance.
    Google Scholar
    suggested: (Google Scholar, RRID:SCR_008878)
    The forest plots were constructed using metaprop package in STATA.
    STATA
    suggested: (Stata, RRID:SCR_012763)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).


    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Limitations: Even though we limited the review to articles in English, very few studies were excluded for that reason. We could not include studies from Asia and South America because of incomplete data of cases tested in 2019, even after contacting the corresponding authors. Another limitation was the inaccuracy in the catchment population for hospital-based and non-sentinel surveillances. Due to a lack of studies enrolling all age groups from Japan, one hospital-based study among paediatric cases had to be included for the quantitative synthesis.

    Results from TrialIdentifier: No clinical trial numbers were referenced.


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: We did not find any issues relating to colormaps.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.


    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.