Problematic has become outdated in relation with current litterature advances.

Cytomegalovirus is a herpesviridae whose prevalence in general population is between 50 to 80%. In immunocompetent individuals, CMV remains latent in a number of cells, without any pathological consequence. Immunosuppression may reactivate the virus causing either a CMV-active infection or a CMV disease with attributable symptoms.

In Intensive Care Unit (ICU), 6 to 30 % of critically ill patients without classical immunosuppression, as those suffering from septic shock, present CMV reactivation. Our aim is to study the risk factors for developing viremia or CMV disease in ICU patients in septic shock without previous immunodepression and determine the relationship between viral reactivation and this acquired immunity alteration.

Immunosuppression statuses causing both CMV active infection or disease are mainly consecutive to HIV infection, bone marrow or solid organ transplantation. However, in severely ill patients, as in septic shock, it has been proved that after a hyper-inflammatory phase occurred a negative control of the immunity, resulting in a paralysed or impaired immune system. The length and extent of this immunodeficiency is correlated with the duration of ICU stay, the occurrence of nosocomial infection and mortality.

A better understanding of CMV's natural history reactivation in the critically ill patient would better define the benefits from a specific therapy.

Inclusion Criteria:

• 18 years or older
• ICU admission for more than 3 days
• Admission for septic shock
• Patient with mechanical invasive ventilation

Exclusion Criteria:

• Immunodepression status before ICU admission (chemotherapy, bone marrow or solid organ transplantation, long time corticosteroid treatment, immunosuppressant therapy, HIV infection)
• Seronegative patient for CMV
• Patient under anti-virus treatment
• Patient under guardianship

Patients admitted in ICU for septic shock, without previous immunodepression, and who will stay in ICU for over 3 days, mechanically ventialted