Abstract
Critically ill patients are admitted to an intensive care unit (ICU) for multiple
reasons. In this study, we aim to analyze the current evidence and findings associated
with influenza and other emergent viral infections, namely, herpes simplex virus type
1 (HSV-1), Epstein-Barr virus (EBV), and cytomegalovirus (CMV).
Among medical conditions, community-acquired respiratory infections are the most frequent
reason for ventilatory support in ICUs. Community-acquired pneumonia in a severe form
including the need of invasive mechanical ventilation and/or vasopressors is associated
with high mortality rates. However, after the pandemic that occurred in 2009 by H1N1
influenza, the number of cases being admitted to ICUs with viral infections is on
the rise. Patients in whom an etiology would not have been identified in the past
are currently being tested with more sensitive viral molecular diagnostic tools, and
patients being admitted to ICUs have more preexisting medical conditions that can
predispose to viral infections. Viral infections can trigger the dysregulation of
the immune system by inducing a massive cytokine response. This cytokine storm can
cause endothelial damage and dysfunction, deregulation of coagulation, and, consequently,
alteration of microvascular permeability, tissue edema, and shock. In severe influenza,
this vascular hyperpermeability can lead to acute lung injury, multiorgan failure,
and encephalopathy. In immunocompetent patients, the most common viral infections
are respiratory, and influenza should be considered in patients with severe respiratory
failure being admitted to ICU. Seasonality and coinfection are two important features
when considering influenza as a pathogen in critically ill patients.
Herpesviridae (HSV, CMV, and EBV) may reactivate in ICU patients, and their reactivation
is associated with morbidity/mortality. However, whether a specific treatment may
impact on outcome remains to be determined.
Keywords
community-acquired respiratory infections - herpesviridae - intensive care unit