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Observational Study
. 2022 Oct;15(10):1118-1123.
doi: 10.1016/j.jiph.2022.08.021. Epub 2022 Sep 7.

Nosocomial acquisition of influenza is associated with significant morbidity and mortality: Results of a prospective observational study

L B Snell  1 , J P Vink  2 , N Q Verlander  3 , S Miah  3 , A Lackenby  3 , D Williams  3 , H Mitchell  4 , C Beviz  4 , M Kabia  4 , E Cunningham  5 , R Batra  2 , J D Edgeworth  6 , M Zambon  3 , G Nebbia  6
Affiliations
Observational Study

Nosocomial acquisition of influenza is associated with significant morbidity and mortality: Results of a prospective observational study

L B Snell et al. J Infect Public Health. 2022 Oct.

Abstract

Background: Nosocomial acquisition of influenza is known to occur but the risk after exposure to a known case and the outcomes after acquisition are poorly defined.

Methods: Prospective observational study of patients exposed to influenza from another patient in a multi-site healthcare organisation, with follow-up of 7 days or until discharge, and PCR-confirmation of symptomatic disease. Multivariable analysis was used to investigate association of influenza acquisition with high dependency unit/intensive care unit (HDU/ITU) admission and in-hospital mortality.

Results: 23/298 (7.7%) contacts of 11 cases were subsequently symptomatic and tested influenza-positive during follow-up. HDU/ITU admission was significantly higher in these secondary cases (6/23, 26%) compared to flu-negative contacts (20/275, 7.2%; p = 0.002). In-hospital mortality was significantly higher in secondary cases (5/23, 21.7%) compared to flu-negative contacts (11/275, 4%; p < 0.001). In multivariable analysis, age (OR 1.25 95% CI: 1.01-1.54, p = 0.02) and being a secondary case (OR 4.77, 95% CI: 1.63-13.9, p = 0.008) were significantly associated with HDU/ITU admission in contacts. Age (OR 1.00, 95% CI: 0.93-1.00, p = 0.02), being a secondary case after exposure to influenza (OR 3.81, 95% CI 1.09-13.3, p = 0.049) and co-morbidity (OR 1.29 per unit increment in the Charlson score, 95% CI 1.02-1.61, p = 0.03) were significantly associated with in-hospital mortality in contacts.

Conclusions: Nosocomial acquisition of influenza was significantly associated with increased risk of HDU/ITU admission and in-hospital mortality.

Keywords: Hospital-acquired infection; Infection prevention and control; Influenza.

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Conflict of interest statement

Conflicts of interest None.

Figures

Fig. 1
Fig. 1
Flow chart of influenza cases and contacts identified during the study period.
Fig. 2
Fig. 2
Maximum likelihood phylogenetic tree of whole genome sequences of influenza of H1N1 subtype from residual samples. Branches are labelled with anonymous patient identification number. Branches where viral genomes show high relatedness are coloured in red. Cases use black font colour; secondary cases blue font colour. Cases or secondary cases which are the only member of their prospectively identified epidemiological clusters represented on the phylogeny are marked with a purple asterisk. Cases and secondary cases linked by both epidemiological and genomic analysis are grouped with a green box. Where the box has a dashed outline this represents cryptic transmission.
Fig. 3
Fig. 3
Maximum likelihood phylogenetic tree of whole genome sequences of influenza of H3N2 subtype from residual samples. Branches are labelled with anonymous patient identification number. Branches where viral genomes show high relatedness are coloured in red. Cases use black font colour; secondary cases blue font colour. Cases or secondary cases which are the only member of their prospectively identified epidemiological clusters represented on the phylogeny are marked with a purple asterisk. Cases and secondary cases linked by both epidemiological and genomic analysis are grouped with a green box.
See this image and copyright information in PMC

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