The new Severe acute respiratory syndrome coronavirus (SARS-CoV-2) named coronavirus disease 2019 (COVID-19) is currently responsible for a pandemic spread of febrile respiratory infections, responsible for a veritable global health crisis.

In adults, several evolutionary patterns are observed: i) a/pauci-symptomatic forms; ii) severe forms immediately linked to rare extensive viral pneumonia; and iii) forms of moderate severity, some of which progress to secondary aggravation (Day 7-Day 10). Children can be affected, but are more rarely symptomatic and severe pediatric forms are exceptional.

Like some other coronaviruses (SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV)), these differences in clinical expression could be based on a variability in the immunological response, notably either via inhibition of the type I interferon (IFN-I) response, or on the contrary an immunological dysregulation responsible for a "cytokine storm" associated with the aggravation. Little is known about the impact of these innate immune response abnormalities on the adaptive response. In addition, certain genetic factors predisposing to a state of "hyper-fragility" and certain viral virulence factors could also be predictive of the clinical response.

In this context, the main hypothesis is that the virological analysis and the initial biological and immunological profiles are correlated with the initial clinical presentation of COVID-19 infection. In particular, children forms and pauci-symptomatic disease in adults may be linked to a more robust innate immune response, including better production of IFN-I.

Inclusion Criteria:

Group E1:

• Age from birth to <18 years old;
• Weight> 3 kilogram (kg);
• Infection with SARS-CoV-2 virus confirmed by RT-PCR on upper respiratory tract sample
• No fever or respiratory symptoms;
• Not requiring hospitalization (or hospitalization not related to a SARS-CoV-2 infection);
• Consent signed by at least one parent / holder of parental authority and assent of the child (if applicable);
• Beneficiary of a social security scheme

Group E2:

• Age from birth to <18 years old;
• Weight> 3kg;
• Infection with the SARS-CoV-2 virus confirmed by RT-PCR on a upper or low respiratory tract sample or pneumonia with scanner suggesting SARS-CoV-2 infection;
• Hospitalized in a pediatric intensive care unit or in a general pediatrics unit
• Consent signed by at least one parent / holder of parental authority and assent of the child (if applicable);
• Beneficiary of a social security scheme

Group E3:

• Age from birth to <18 years old;
• Weight> 3 kg;
• Negative SARS-CoV-2 PCR on at least one respiratory sample, and other confirmed viral infection
• Hospitalized in a pediatric intensive care unit or in a general pediatrics unit, for a respiratory reason;
• Consent signed by at least one parent / holder of parental authority and assent of the child (if applicable);
• Beneficiary of a social security scheme

Exclusion Criteria:

Group E1:

• Patients with any other inherited or acquired immune deficiency that could compromise the immunological evaluation;
• Other Suspected or proved infection
• Pregnancy.

Group E2:

• Patients with any other inherited or acquired immune deficiency that could compromise the immunological evaluation;
• Pregnancy.

Group E3:

• Patients with any other inherited or acquired immune deficiency that could compromise the immunological evaluation;
• Infection with the SARS-CoV-2 virus known among the relatives
• Pregnancy.