Abstract: the natural variability of influenza viruses, manifested in changes in surface antigens, leads to the emergence of new highly pathogenic strains of “bird” and “pig” origin. This complicates the epidemic situation and requires a thorough study of the antigenic characteristics of newly emerging pathogens. Influenza caused by different strains in recent years, while maintaining the main clinical manifestations, has a number of significant features, which is expressed in the varying severity and duration of clinical syndromes. In the age structure of the incidence of influenza and ARVI in the Novgorod region is dominated by children under 17 years. The morbidity of the child population (by age groups) was 4-5.7 times higher than that of the population as a whole. The material of the study was: cylindrical epithelial cells from the mucous nasal passages and flat epithelial cells from the posterior pharyngeal wall, processed according to the standard procedure for detecting antigens of influenza and ARVI viruses and determining the etiology of the disease. As a result of the analysis for the period 2013-2017 in the Novgorod region there was an active circulation of viruses of non-influenza etiology in the pre-epidemic period and during the influenza epidemic. A parallel study of biomaterial from patients and persons with suspected influenza and ARVI by express methods, followed by isolation of the virus on the culture of MDCK tissue cells, is more effective for indicating strains of influenza A and B viruses. Monitoring of influenza incidence showed simultaneous circulation of two subtypes: influenza A virus and influenza B, with predominance of A type influenza.

Keywords: influenza, ARVI, virus etiology, immunofluorescence method, monitoring