Background
The pathophysiology of influenza virus infection
Host and viral mechanisms of influenza-associated pathology | ||
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Direct viral induced pathology | Innate immune responses | Adaptive immune responses |
• Epithelial cell death (apoptosis and necrosis) • Alveolar compromise • Denudation of the airways | • Local and systemic cytokine production • Innate immune cellular infiltration (neutrophils, inflammatory monocytes) • Extracellular matrix degradation | • Exuberant T cell responses (CD4 and CD8) • Excess cytokine production • Immune-cell mediated epithelial denudation • Amplification of inflammation and local and systemic cytokine production |
How influenza triggers ARDS
Influenza clinical progression to pneumonia and ARDS
Influenza presenting as sepsis
Role of viral-bacterial co-infections and their effect on outcomes
Other less common severe complications of Influenza
Severe influenza complications | |
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Influenza pneumonia | |
Secondary bacterial pneumonia | |
ARDS | |
Influenza sepsis | |
Secondary bacterial sepsis | |
Myositis and rhabdomyolysis | |
Acute myocarditis | |
Acute pericarditis | |
Acute encephalitis | |
Acute disseminated encephalomyelitis | |
Transverse myelitis | |
Aseptic meningitis | |
Guillain-Barre syndrome |
Conclusions
Acknowledgements
Summary figure
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Influenza virus affects the respiratory tract by direct viral infection or by damage from the immune system response.
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Approximately 30–40% of hospitalized patients with laboratory-confirmed influenza are diagnosed with acute pneumonia.
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Coinfections with other viruses and bacteria are common.
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Influenza should be suspected not only in patients with typical symptoms and epidemiology, but also in patients with severe pneumonia, ARDS, sepsis, encephalitis, myocarditis, and rhabdomyolysis.