This study is a prospective, multicentric, observational test negative design study on adults hospitalized for Severe Acute Respiratory Infection (SARI), regardless of their vaccination status.

Participation to the study will be systematically proposed to all patients hospitalized fitting inclusion criteria. Patient's screening will be done in emergency department or hospital department with direct admission. Medical investigators explain the objectives of the studies, procedure and propose the patient to participate in the study. Socio-demographic data, clinical and virological data will be collected in an electronic clinical research form.

A follow-up at 1 and 3 months after hospitalization discharge will be scheduled to evaluate health status.

The remainder of respiratory samples that have been performed for care will be used for further testing depending on epidemiological situation and will be stored at -80°C.

Inclusion Criteria:

• Age ≥ 18 years old
• Admitted in a hospital for at least 24 h
• Presents SARI criteria within onset within the last 14 days before sampling and less than 48 h after hospitalisations:

At least one of the following signs (without treatment): fever or feverishness, malaise, headache, myalgia or sign of fatigue (loss of weight or anorexia or confusion or dizziness) Associated with at least one respiratory symptom or sign (cough, sore throat or shortness of breath; or tachypnoea or signs of low oxygen saturation)

• completed non-opposition form
• Respiratory samples within 14 days after symptoms onset, in the context of care

Exclusion Criteria:

• Contraindication of vaccination

Hospitalized patients presenting with SARI symptom onset in the first 14 days