Objective. To study the features of the clinic and serological diagnosis of pertussis in adults. Patients and methods. The study included patients admitted to Infectious diseases clinical hospital No 1 in 2018 with prolonged cough syndrome. Clinical methods were used for monitoring adult patients with pertussis. Information about the course of the disease is recorded in the "case histories" and clinical observation cards. To verify whooping cough, blood was examined to detect anti-pertussis antibodies of class IgM, IgG, IgA using an enzyme-linked immunosorbent assay (RIDASCRЕЕN, R-Bioрharm AG). Results. In total, 52 patients were included in the study, among which pertussis was verified in 57.7–6.8% of patients. Using the generally accepted classification in 26.6–8.0% of patients, pertussis proceeded in a mild form, in 66.7–8.6% in moderate and in 6.7–4.5% in severe form. The presented clinical characteristics of pertussis in adults debunk the myth of the supposedly mild course of the disease in this population. A description of the severe course of whooping cough in an elderly patient is presented. A feature of the formation of post-infectious immunity in adults is, along with the development of IgG class antibodies starting from the 3rd week of the disease, the rapid accumulation of IgA class antibodies in the absence of IgM class antibodies. Conclusion. A detailed description of the clinical symptoms of pertussis in adults will improve the doctors' awareness of the clinical verification of pertussis. The effectiveness and prospects of using the enzyme-linked immunosorbent assay for the diagnosis of pertussis in adults with a single study, starting from the 3rd week from the onset of the disease, are proved. Key words: ELISA, whooping cough, clinical forms, serological diagnosis, severity of course

Subacute thyroiditis is a relatively rare thyroid disease that develops after acute viral upper respiratory tract infection and manifests with neck pain, fever and transient hyperthyroidism. The diagnosis is often delayed due to the non-specific presentation and laboratory findings. It is misdiagnosed with upper respiratory tract infections, cervical lymph-adenitis, even with acute pyelonephritis. The authors present a series of 12 patients with subacute thyroiditis and discuss the main steps in the diagnosis, differential diagnosis and treatment of this disease.