Viral infections in the ICU

Purpose of review The present study reviews the precise role of viruses as causes of pneumonia in mechanically ventilated patients. Recent findings In patients requiring mechanical ventilation, Herpesviridae, mostly herpes simplex virus and cytomegalovirus, are commonly recovered from the respiratory tract. However, viral detection does not necessarily mean viral disease, and the exact role of viruses recovered in the respiratory tract is still being debated. Are they only benign colonizers activated in proportion to the severity of the underlying illness, or are they infectious agents with true attributable morbidity or mortality or both? Summary Respiratory viruses are responsible for 10% of community-acquired pneumonia cases but do not cause nosocomial pneumonia. Herpesviridae, mainly herpes simplex virus and cytomegalovirus, are commonly detected in the respiratory tract of nonimmunocompromised,mechanically ventilated patients. Although their detection usually reflects viral reactivation without lung parenchymal involvement, in a particular subset of patients, viral lung disease (bronchopneumonitis) occurs. This bronchopneumonitis seems to have a true impact on outcome, but only interventional studies will be able to determine its real impact. Whether other viruses, such as mimivirus, are responsible for nosocomial pneumonia in mechanically ventilated patients requires additional studies.