Impact of Latent Viral Infections in Mechanically Ventilated Patients

Cytomegalovirus (CMV), herpes simplex virus (HSV) type 1 (HSV-1) and type 2 (HSV-2), human herpes virus 6 (HHV-6) and 7 (HHV-7) and Epstein-Barr virus (EBV) all belong to the family of herpesviridae, are highly prevalent and ubiquitously distributed. In the immunocompetent adult host CMV and HSV infections usually have a benign course. As is the case with other herpesviridae, the initial infection is followed by a lifelong latent infection from which reactivation can occur. Asymptomatic viral shedding of CMV and/or HSV may occur in immunocompetent individuals. This viral shedding in patients without active viral disease makes it difficult to diagnose active disease in patients. In immunocompromised patients severe active disease due to these viruses is known to occur. However, critically ill patients admitted to the intensive care unit (ICU) are considered immunocompetent. Recent studies suggest that active infection with CMV, HSV, EBV or HHV-6 is also relatively common in ICU patients. Furthermore, an association between the presence of a CMV or HSV infection and increased mortality in critically ill patients was found. At present it is not clear whether this is intrinsically related to the micro-organism itself or merely an indication of the patients deteriorating physical condition leading to viral reactivation. To date the value of ganciclovir and acyclovir prophylaxis and/or treatment is unclear. The clinical relevance of active EBV or HHV-6 infection has not been established yet.