The role of pneumonia and secondary bacterial infection in fatal and serious outcomes of pandemic influenza a(H1N1)pdm09

Chandini Raina MacIntyre, Abrar Ahmad Chughtai, Michelle Barnes, Iman Ridda, Holly Seale, Renin Toms, Anita Heywood, Chandini Raina MacIntyre, Abrar Ahmad Chughtai, Michelle Barnes, Iman Ridda, Holly Seale, Renin Toms, Anita Heywood

Abstract

Background: The aim of this study was to estimate the prevalence of pneumonia and secondary bacterial infections during the pandemic of influenza A(H1N1)pdm09.

Methods: A systematic review was conducted to identify relevant literature in which clinical outcomes of pandemic influenza A(H1N1)pdm09 infection were described. Published studies (between 01/01/2009 and 05/07/2012) describing cases of fatal or hospitalised A(H1N1)pdm09 and including data on bacterial testing or co-infection.

Results: Seventy five studies met the inclusion criteria. Fatal cases with autopsy specimen testing were reported in 11 studies, in which any co-infection was identified in 23% of cases (Streptococcus pneumoniae 29%). Eleven studies reported bacterial co-infection among hospitalised cases of A(H1N1)2009pdm with confirmed pneumonia, with a mean of 19% positive for bacteria (Streptococcus pneumoniae 54%). Of 16 studies of intensive care unit (ICU) patients, bacterial co-infection identified in a mean of 19% of cases (Streptococcus pneumoniae 26%). The mean prevalence of bacterial co-infection was 12% in studies of hospitalised patients not requiring ICU (Streptococcus pneumoniae 33%) and 16% in studies of paediatric patients hospitalised in general or pediatric intensive care unit (PICU) wards (Streptococcus pneumoniae 16%).

Conclusion: We found that few studies of the 2009 influenza pandemic reported on bacterial complications and testing. Of studies which did report on this, secondary bacterial infection was identified in almost one in four patients, with Streptococcus pneumoniae the most common bacteria identified. Bacterial complications were associated with serious outcomes such as death and admission to intensive care. Prevention and treatment of bacterial secondary infection should be an integral part of pandemic planning, and improved uptake of routine pneumococcal vaccination in adults with an indication may reduce the impact of a pandemic.

Keywords: Bacterial infection; Influenza A(H1N1)pdm09; Pneumonia; Respiratory infections hospitalization.

Conflict of interest statement

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

C. Raina MacIntyre has received in-kind support and funding for investigator-driven research from GlaxoSmithKline, Pfizer, Merck, and Seqirus, and has sat on advisory boards for Merck, GlaxoSmithKline and Pfizer. IR: IR has received grant funds for investigator-driven research from GSK, Pfizer and for consultation from Merck. The remaining authors declare that they have no competing interests and have no non-financial interests that may be relevant to the submitted work.

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Figures

Fig. 1
Fig. 1
Study diagram
Fig. 2
Fig. 2
Average prevalence of bacterial infection in fatal, ICU admitted, general ward admitted and paediatric patients

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