What role do viruses play in nosocomial pneumonia?
OBJECTIVE
Viruses are an increasingly recognized cause of community-acquired pneumonia (CAP), but their exact role in nosocomial pneumonia is still debated. This review focuses on the role of viruses as a cause of nosocomial pneumonia.


RESULTS
Respiratory viruses may be responsible for healthcare-associated pneumonia, because affected patients and those with CAP have the same risk factors for viral disease. In mechanically ventilated patients, viruses belonging to the Herpesviridae family, namely herpes simplex virus (HSV) and cytomegalovirus, can be reactivated and cause bronchopneumonitis or ventilator-associated pneumonia, respectively. Recent results confirmed the high rate of HSV reactivation in the distal airways of mechanically ventilated patients, and that patients with high virus loads (>10(5)  copies/ml of bronchoalveolar lavage fluid) have poorer outcomes than those with low or no virus load. However, the responsibility of mimivirus, initially described as a possible cause of pneumonia, was not confirmed for nosocomial pneumonia.


CONCLUSIONS
Respiratory viruses are mainly responsible for CAP, but they may also cause healthcare-associated pneumonia. HSV bronchopneumonitis and cytomegalovirus pneumonia are not rare diseases, and patients with Herpesviridae lung infections have worse prognoses than those without. Whether or not those Herpesviridae infections are responsible for true morbidity or morbidity remains to be determined.
Service de Réanimation Médicale, Institut de Cardiologie, Groupe Hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, and Université Paris 6-Pierre et Marie Curie, Paris, France.
Charles-Edouard
CE
Luyt
Nicolas
N
Bréchot
Jean
J
Chastre
D017714:Community-Acquired Infections / Q000821:virology*; D003428:Cross Infection / Q000821:virology*; D003586:Cytomegalovirus Infections / Q000821:virology; D006566:Herpesviridae Infections / Q000821:virology; D006801:Humans; D011024:Pneumonia, Viral / Q000209:etiology*; D012307:Risk Factors; D014775:Virus Activation