Cited by 524Influenza Virus Research StudiesRespiratory Support and MechanismsRespiratory viral infections research

Influenza virus-related critical illness: pathophysiology and epidemiology

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Kalil, Andre C., Thomas, Paul G.·2019·Critical Care

Abstract

Influenza virus affects the respiratory tract by direct viral infection or by damage from the immune system response. In humans, the respiratory epithelium is the only site where the hemagglutinin (HA) molecule is effectively cleaved, generating infectious virus particles. Virus transmission occurs through a susceptible individual's contact with aerosols or respiratory fomites from an infected individual. The inability of the lung to perform its primary function of gas exchange can result from multiple mechanisms, including obstruction of the airways, loss of alveolar structure, loss of lung epithelial integrity from direct epithelial cell killing, and degradation of the critical extracellular matrix.Approximately 30-40% of hospitalized patients with laboratory-confirmed influenza are diagnosed with acute pneumonia. These patients who develop pneumonia are more likely to be < 5 years old, > 65 years old, Caucasian, and nursing home residents; have chronic lung or heart disease and history of smoking, and are immunocompromised.Influenza can primarily cause severe pneumonia, but it can also present in conjunction with or be followed by a secondary bacterial infection, most commonly by Staphylococcus aureus and Streptococcus pneumoniae. Influenza is associated with a high predisposition to bacterial sepsis and ARDS. Viral infections presenting concurrently with bacterial pneumonia are now known to occur with a frequency of 30-50% in both adult and pediatric populations. The H3N2 subtype has been associated with unprecedented high levels of intensive care unit (ICU) admission.Influenza A is the predominant viral etiology of acute respiratory distress syndrome (ARDS) in adults. Risk factors independently associated with ARDS are age between 36 and 55 years old, pregnancy, and obesity, while protective factors are female sex, influenza vaccination, and infections with Influenza A (H3N2) or Influenza B viruses.In the ICU, particularly during the winter season, influenza should be suspected not only in patients with typical symptoms and epidemiology, but also in patients with severe pneumonia, ARDS, sepsis with or without bacterial co-infection, as well as in patients with encephalitis, myocarditis, and rhabdomyolysis.

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  • Human influenza A, B, and C viruses primarily attach to and replicate within respiratory epithelial cells that line the upper to lower respiratory tract.

    “Human influenza A, B, and C viruses primarily attach to and replicate within respiratory epithelial cells that line the upper to lower respiratory tract [158].”
  • Risk factors associated with influenza disease severity include extreme age and comorbidities (chronic cardiorespiratory diseases).

    “Risk factors associated with disease severity include extreme age and patients with comorbidities (chronic cardiorespiratory diseases) [158].”
  • Influenza viruses primarily attach to and replicate within respiratory epithelial cells from upper to lower respiratory tract.

    “These viruses primarily attach to, and replicate within, respiratory epithelial cells running from the upper (nasal cavity, oral cavity, pharynx, larynx) to lower respiratory tract (trachea, bronchi, bronchioles and alveoli) (Kalil and Thomas, 2019).”

    From Viral Infections, the Microbiome, and Probiotics (2021) · cites this paper as Kalil and Thomas, 2019

  • Predominant determinant of severity of influenza disease is extent to which lower respiratory tract becomes breached by virus; risk factors include extremes of age (<5 and >65), Caucasians, and comorbid chronic cardiorespiratory diagnoses.

    “The predominant determinate of the severity of associated disease is the extent to which the lower respiratory tract becomes breached by the virus, risk factors for which include extremes of age (<5 years and > 65 years), Caucasians and comorbid chronic cardiorespiratory diagnoses (Kalil and Thomas, 2019).”

    From Viral Infections, the Microbiome, and Probiotics (2021) · cites this paper as Kalil and Thomas, 2019

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Authors
Kalil, A. C., & Thomas, P. G.
Affiliations
St. Jude Children's Research Hospital (US)
Venue
Critical Care
Published
2019-07-19
Volume
23
Issue
1
Pages
258-258
ISSN
1364-8535 (ISSN-L)
OpenAlex
W2963276598
Cited by
524
References
89
Citations by year
2026: 60 · 2025: 61 · 2024: 95 · 2023: 91 · 2022: 75 · 2021: 74 · 2020: 62 · 2019: 5 · 2015: 1
FWCI
7.88
Type
journal article
Language
en
Open access
Locations
  • Critical Care (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Topics
  • Health Sciences › Medicine › Epidemiology › Influenza Virus Research Studies
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Respiratory Support and Mechanisms
  • Health Sciences › Medicine › Epidemiology › Respiratory viral infections research
Keywords
influenza virus, critical illness, acute respiratory distress syndrome, influenza-associated pneumonia, bacterial co-infection, sepsis, hemagglutinin cleavage, extracellular matrix degradation, H3N2, intensive care unit admission, risk factors, influenza vaccination, influenza epidemiology
MeSH terms
Adult, Female, Humans, Influenza, Human, Influenza Vaccines, Middle Aged, Obesity, Orthomyxoviridae, Respiratory Distress Syndrome, Sex Factors, Critical Illness, Sepsis, Protective Factors

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