INCLUSION CRITERIA  To be eligible, study patients must meet the following criteria:  For cases:  Be at least 18 years of age Have an RT-PCR confirmed SARS-CoV-2 infection within 72 hours prior to inclusion. Have given informed consent or that of their guardian/ representative to participate in the study.  Diagnosed as a severe COVID-19 case according to the following criteria:  Presenting clinical signs of pneumonia: fever, cough, dyspnea or crepitations AND Presenting at least one of the following signs:  Respiratory rate > 30 cycles/min OR Severe respiratory distress or SpO2 < 90% on room air  Be admitted to a care unit for COVID-19 Residing in the health zone for at least 6 months  For controls:  Be at least 18 years of age Have a PCR-confirmed SARS-CoV-2 infection within 72 hours prior to inclusion Have given informed consent to participate in the study  Diagnosed as a non-severe COVID-19 case according to the following criteria:  Be asymptomatic OR Symptomatic, but no evidence of severe pneumonia Respiratory rate > 30 cycles/min OR Severe respiratory distress or SpO2 < 90% on room air Not be admitted to a care unit for COVID-19. Reside in the study health area for at least 6 months  EXCLUSION CRITERIA  To be eligible, study patients cannot meet the following criteria for cases and controls:  Subject has a contraindication to venipuncture, as determined by clinical judgment Subject is vaccinated against SARS-CoV-2 Subject has been infected with SARS-CoV-2 in the past and now presents with reinfection