Inclusion Criteria:  For all groups:  Informed consent signed by the patient. Men and women aged 18 and over.  Group COVID-19 (asymptomatic):  Confirmed diagnosis of COVID-19 (positive SARS-CoV-2 RNA PCR test or history of IgM and / or IgG antibodies to SARS-CoV-2) Absence of any clinical symptoms associated with coronavirus infection.  Group Healthy:  Contact with patients with symptomatic new coronavirus infection COVID-19 in the absence of personal protective equipment for at least 3 days. Absence of any clinical symptoms associated with coronavirus infection  Group COVID symptomatic:  Confirmed diagnosis of previous COVID-19 (positive SARS-CoV-2 RNA PCR test or presence of IgM antibodies to SARS-CoV-2) in history.  A severe course of COVID-19, characterized by one or more of the following symptoms:  Respiratory rate ≥ 30 in 1 min Blood oxygen saturation (SpO2) ≤ 93% The ratio of the partial tension of oxygen in arterial blood to the fraction of oxygen during inspiration (PaO2 / FiO2) <300 Lung tissue lesion> 50% and / or according to computed tomography CT-2 and higher Septic shock / sepsis Development of multiple organ failure Cytokine storm  Exclusion Criteria:  Pregnancy Covid-19 vaccination Any serious medical illness before coronavirus infection, as well as a permanent form of atrial fibrillation Regular intake of anti-inflammatory, antibacterial, cytostatic and immunosuppressive drugs Refusal to participate in the study