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High one-year mortality following intensive care among adults with influenza A(H1N1)pdm09, A(H3N2), or B in Southern Sweden : a retrospective observational study

Jaffer Broman, Nora LU ; Nilsson, Anna C. LU ; Lengquist, Maria LU orcid ; Frigyesi, Attila LU ; Friberg, Hans LU and Reepalu, Anton LU orcid (2025) In Infectious Diseases 57(12). p.1154-1165
Abstract

Background: Influenza ranges from a mild and self-limiting infection to a life-threatening disease with high mortality despite intensive care. Conclusive data on the association between influenza type/subtype and mortality among adults treated at intensive care units (ICU) is lacking. Objectives: To investigate the mortality in adults admitted to ICU with laboratory-confirmed influenza during three consecutive influenza seasons. Methods: This observational multicenter study included adults with PCR-confirmed influenza requiring intensive care at four hospitals in southern Sweden between 2015–2018. The primary outcome was all-cause one-year mortality. Patient characteristics and the impact of influenza type/subtype were studied using... (More)

Background: Influenza ranges from a mild and self-limiting infection to a life-threatening disease with high mortality despite intensive care. Conclusive data on the association between influenza type/subtype and mortality among adults treated at intensive care units (ICU) is lacking. Objectives: To investigate the mortality in adults admitted to ICU with laboratory-confirmed influenza during three consecutive influenza seasons. Methods: This observational multicenter study included adults with PCR-confirmed influenza requiring intensive care at four hospitals in southern Sweden between 2015–2018. The primary outcome was all-cause one-year mortality. Patient characteristics and the impact of influenza type/subtype were studied using Kaplan–Meier and logistic regression analyses. Results: A total of 146 individuals were included: median age 67 years (interquartile range 56–74), 54% were male. Influenza type/subtype was available for 144/146 (99%); A(H1N1)pdm09 in 50 (35%), A(H3N2) in 37 (26%), and B in 57 (40%) patients. Mortality was 19% in the ICU and 32% before hospital discharge. At one year, 43% were deceased, ranging from 36% to 49%, depending on type/subtype (log-rank test p = 0.32). Mortality rates remained similar for all three influenza types/subtypes after adjusting for age, sex, and a modified comorbidity index. Antibiotics were prescribed for 125/145 (86%) within 48 h of ICU admission, with microbiological confirmation of coinfection in 53/125 (42%). Conclusions: Among adults admitted to intensive care with PCR-confirmed influenza, mortality rates were similar independently of influenza type/subtype. Mortality increased from 19% in the ICU to 43% one year after admission, highlighting the importance of monitoring ICU-survivors and reporting long-term outcomes in critically ill influenza patients.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Influenza A(H1N1)pdm09, influenza A(H3N2;), influenza B, intensive care, long-term outcome, mortality, Sweden
in
Infectious Diseases
volume
57
issue
12
pages
12 pages
publisher
Taylor & Francis
external identifiers
  • pmid:40693835
  • scopus:105011259405
ISSN
2374-4235
DOI
10.1080/23744235.2025.2535443
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
id
b7dec31a-bb0c-4f87-bd84-c84e7be3d530
date added to LUP
2026-01-08 14:10:11
date last changed
2026-01-09 03:14:29
@article{b7dec31a-bb0c-4f87-bd84-c84e7be3d530,
  abstract     = {{<p>Background: Influenza ranges from a mild and self-limiting infection to a life-threatening disease with high mortality despite intensive care. Conclusive data on the association between influenza type/subtype and mortality among adults treated at intensive care units (ICU) is lacking. Objectives: To investigate the mortality in adults admitted to ICU with laboratory-confirmed influenza during three consecutive influenza seasons. Methods: This observational multicenter study included adults with PCR-confirmed influenza requiring intensive care at four hospitals in southern Sweden between 2015–2018. The primary outcome was all-cause one-year mortality. Patient characteristics and the impact of influenza type/subtype were studied using Kaplan–Meier and logistic regression analyses. Results: A total of 146 individuals were included: median age 67 years (interquartile range 56–74), 54% were male. Influenza type/subtype was available for 144/146 (99%); A(H1N1)pdm09 in 50 (35%), A(H3N2) in 37 (26%), and B in 57 (40%) patients. Mortality was 19% in the ICU and 32% before hospital discharge. At one year, 43% were deceased, ranging from 36% to 49%, depending on type/subtype (log-rank test p = 0.32). Mortality rates remained similar for all three influenza types/subtypes after adjusting for age, sex, and a modified comorbidity index. Antibiotics were prescribed for 125/145 (86%) within 48 h of ICU admission, with microbiological confirmation of coinfection in 53/125 (42%). Conclusions: Among adults admitted to intensive care with PCR-confirmed influenza, mortality rates were similar independently of influenza type/subtype. Mortality increased from 19% in the ICU to 43% one year after admission, highlighting the importance of monitoring ICU-survivors and reporting long-term outcomes in critically ill influenza patients.</p>}},
  author       = {{Jaffer Broman, Nora and Nilsson, Anna C. and Lengquist, Maria and Frigyesi, Attila and Friberg, Hans and Reepalu, Anton}},
  issn         = {{2374-4235}},
  keywords     = {{Influenza A(H1N1)pdm09; influenza A(H3N2;), influenza B; intensive care; long-term outcome; mortality; Sweden}},
  language     = {{eng}},
  number       = {{12}},
  pages        = {{1154--1165}},
  publisher    = {{Taylor & Francis}},
  series       = {{Infectious Diseases}},
  title        = {{High one-year mortality following intensive care among adults with influenza A(H1N1)pdm09, A(H3N2), or B in Southern Sweden : a retrospective observational study}},
  url          = {{http://dx.doi.org/10.1080/23744235.2025.2535443}},
  doi          = {{10.1080/23744235.2025.2535443}},
  volume       = {{57}},
  year         = {{2025}},
}