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Influenza A subtype H3N2 is associated with an increased risk of hospital dissemination – an observational study over six influenza seasons

Rothman, E. ; Olsson, O. LU orcid ; Christiansen, C. B. LU ; Rööst, M. LU ; Inghammar, M. LU and Karlsson, U. LU (2023) In Journal of Hospital Infection 139. p.134-140
Abstract

Background: Previous studies on hospital-acquired influenza (HAI) have not systematically evaluated the possible impact of different influenza subtypes. HAI has historically been associated with high mortality, but clinical consequences may be less severe in a modern hospital setting. Aims: To identify and quantify HAI for each season, investigate possible associations with varying influenza subtypes, and to determine HAI-associated mortality. Methods: All influenza-PCR-positive adult patients (>18 years old) hospitalized in Skåne County during 2013–2019, were prospectively included in the study. Positive influenza samples were subtyped. Medical records of patients with suspected HAI were examined to confirm a nosocomial origin and... (More)

Background: Previous studies on hospital-acquired influenza (HAI) have not systematically evaluated the possible impact of different influenza subtypes. HAI has historically been associated with high mortality, but clinical consequences may be less severe in a modern hospital setting. Aims: To identify and quantify HAI for each season, investigate possible associations with varying influenza subtypes, and to determine HAI-associated mortality. Methods: All influenza-PCR-positive adult patients (>18 years old) hospitalized in Skåne County during 2013–2019, were prospectively included in the study. Positive influenza samples were subtyped. Medical records of patients with suspected HAI were examined to confirm a nosocomial origin and to determine 30-day mortality. Results: Of 4110 hospitalized patients with a positive influenza PCR, 430 (10.5%) were HAI. Influenza A(H3N2) infections were more often HAI (15.1%) than influenza A(H1N1)pdm09, and influenza B (6.3% and 6.8% respectively, P<0.001). The majority of HAI caused by H3N2 were clustered (73.3 %) and were the cause of all 20 hospital outbreaks consisting of ≥4 affected patients. In contrast, the majority of HAI caused by influenza A(H1N1)pdm09 and influenza B were solitary cases (60% and 63.2%, respectively, P<0.001). Mortality associated with HAI was 9.3% and similar between subtypes. Conclusions: HAI caused by influenza A(H3N2) was associated with an increased risk of hospital dissemination. Our study is relevant for future seasonal influenza infection control preparedness and shows that subtyping of influenza may help to define relevant infection control measures. Mortality in HAI remains substantial in a modern hospital setting.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Hospital-acquired influenza, Infection control, Influenza hospital outbreaks, Influenza mortality, Influenza subtypes, Nosocomial influenza
in
Journal of Hospital Infection
volume
139
pages
7 pages
publisher
Elsevier
external identifiers
  • pmid:37419188
  • scopus:85165698378
ISSN
0195-6701
DOI
10.1016/j.jhin.2023.06.024
language
English
LU publication?
yes
id
a6a3c50a-4468-4695-bb70-4888e71a565b
date added to LUP
2023-10-25 15:56:02
date last changed
2024-04-19 02:53:43
@article{a6a3c50a-4468-4695-bb70-4888e71a565b,
  abstract     = {{<p>Background: Previous studies on hospital-acquired influenza (HAI) have not systematically evaluated the possible impact of different influenza subtypes. HAI has historically been associated with high mortality, but clinical consequences may be less severe in a modern hospital setting. Aims: To identify and quantify HAI for each season, investigate possible associations with varying influenza subtypes, and to determine HAI-associated mortality. Methods: All influenza-PCR-positive adult patients (&gt;18 years old) hospitalized in Skåne County during 2013–2019, were prospectively included in the study. Positive influenza samples were subtyped. Medical records of patients with suspected HAI were examined to confirm a nosocomial origin and to determine 30-day mortality. Results: Of 4110 hospitalized patients with a positive influenza PCR, 430 (10.5%) were HAI. Influenza A(H3N2) infections were more often HAI (15.1%) than influenza A(H1N1)pdm09, and influenza B (6.3% and 6.8% respectively, P&lt;0.001). The majority of HAI caused by H3N2 were clustered (73.3 %) and were the cause of all 20 hospital outbreaks consisting of ≥4 affected patients. In contrast, the majority of HAI caused by influenza A(H1N1)pdm09 and influenza B were solitary cases (60% and 63.2%, respectively, P&lt;0.001). Mortality associated with HAI was 9.3% and similar between subtypes. Conclusions: HAI caused by influenza A(H3N2) was associated with an increased risk of hospital dissemination. Our study is relevant for future seasonal influenza infection control preparedness and shows that subtyping of influenza may help to define relevant infection control measures. Mortality in HAI remains substantial in a modern hospital setting.</p>}},
  author       = {{Rothman, E. and Olsson, O. and Christiansen, C. B. and Rööst, M. and Inghammar, M. and Karlsson, U.}},
  issn         = {{0195-6701}},
  keywords     = {{Hospital-acquired influenza; Infection control; Influenza hospital outbreaks; Influenza mortality; Influenza subtypes; Nosocomial influenza}},
  language     = {{eng}},
  pages        = {{134--140}},
  publisher    = {{Elsevier}},
  series       = {{Journal of Hospital Infection}},
  title        = {{Influenza A subtype H3N2 is associated with an increased risk of hospital dissemination – an observational study over six influenza seasons}},
  url          = {{http://dx.doi.org/10.1016/j.jhin.2023.06.024}},
  doi          = {{10.1016/j.jhin.2023.06.024}},
  volume       = {{139}},
  year         = {{2023}},
}