Inclusion Criteria:  Controls:  - Hospitalized patient with non-SARS-CoV-2 hypoxemic pneumonia  Patients COVID 19:  - Patient hospitalized for SARS-CoV-2 hypoxemic pneumonia  All:  Patient hospitalized for less than 48 hours in a general intensive care unit Patient who has given free, informed and express (oral) consent to participate in the research (or a close relative or trusted person of the patient if the patient cannot express himself/herself) Patient covered by a social security system or equivalent Expected hospitalization of more than 48 hours  Exclusion Criteria:  gut inflammatory disease recent gut surger ostomy recent antibiotics artificial nutrition in the long term