Unlike other respiratory viruses such as influenza and RSV where the child is the essential reservoir and central vector of intrafamilial contamination, the child is likely to be a small player in the transmission of CoV2-CoRSA infection. This study aims to describe the age category of the first contact, within 14 days before the appearance of the first symptoms of the index case in order to describe the age categories of this first contaminant, globally, in the group of children and finally in the group of adults. This work is intended to provide food for discussion and to justify the distancing and containment measures imposed on children when their isolation has a deleterious impact that has now been established for some children.

Inclusion Criteria:

• 1) Children hospitalized in the Pediatric department of the Hospices Civils de Lyon with PCR positive for a variant of the historical SARS-CoV2, 2) Adults hospitalized in the the Hospices Civils de Lyon, for a Covid-19 disease with documented infection by a variant of the SARS-CoV-2 and included in the NOSO-COR study with matching criteria described below.

Exclusion Criteria:

1. Any patient suspected of nosocomial infection.
2. Any patient death during the Covid-19 infection.
3. Any adult patient without children living home.
4. Opposition to participate.

Hospital-based population of children and adults:

• Hospitalized children, 0 to 17 years of age, 25 subjects, consecutive sample survey
• Hospitalized adults, 18 years and above, 50 matched subjects