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.