Morbidity and mortality of ICU patients is increased by the development of a "immunosuppression" systemic (IS). This IS develops in the early hours of hospitalization and is responsible for severe infections, including viral reactivations (Cytomegalovirus or Herpes Simplex Virus). Viral reactivation was associated with increased morbidity and mortality in intensive care units. In clinical practice, they are searched at the onset of organ failure or unexplained fever. The investigators wish to conduct this research in the stroke patients to assess the predictive power of these viral reactivations on the duration of mechanical ventilation.

PCR for herpes simplex virus in blood and in tracheal aspirate (Day-1, Day-7 and Day-15) - clinicians are blinded to the results PCR for Cytomegalovirus in blood and in tracheal aspirate (Day-1, Day-7 and Day-15) - clinicians are blinded to the results

Inclusion Criteria:

• Hospitalisation in intensive care unit
• Acute brain injury (trauma, subarachnoid haemorrhage, stroke, infection) with Glasgow Coma Scale <= 12
• Age between 18 and 75 years
• Mechanical ventilation > 24 hours

Exclusion Criteria:

• encephalopathy post anoxy
• active cancer
• Immunosuppresseur treatment
• pregnancy
• history of autoimmune disease

• Acute brain injury (trauma, subarachnoid haemorrhage, stroke, infection) with Glasgow Coma Scale <= 12
• Age between 18 and 75 years