Features of Long-Term Incidence Rates of Acute Viral Upper Respiratory Tract Infections and Influenza in the Population of the Rostov Region

Introduction: As of today, acute viral upper respiratory tract infections (URTIs) remain the most common diseases in the world and the Russian Federation and one of the most important problems of national health care. The objective of our work was to study the dynamics and intensity of the epidemic process of influenza and other URTIs in the Russian Federation and Rostov Region over a thirty-year period and to establish the main features of the disease incidence in the Rostov Region. Materials and methods: We analyzed data of annual State Reports on Sanitary and Epidemiological Wellbeing of the Population in the Russian Federation and Statistical Form No. 2 on information about infectious and parasitic diseases for the period 1990-2019 and data on the size of population using StatSoft STATISTICA 6.1.478 Russian, Microsoft Excel, and Next-GIS QGIS software. Results: We found that in 1990-1999, 2000-2009, and 2010-2019, regional URTI rates tended to decrease in each subsequent decade compared to the previous one. The long-term incidence rate of URTIs in the Rostov Region was 16,099.2 ± (2.045 x 384.2) %ооо, lower than the Russian average rate of 19,710.3 ± (2.045 x 326.4) (p = 0.05). The amplitude of fluctuations in the incidence was 8,015.4 %ооо and 7,619.6 %ооо in the Rostov Region and the Russian Federation, respectively. Until 1997, regional incidence rates were comparable to the national averages but demonstrated an upward trend since the year 2000. We revealed unevenness of the course of the epidemic process related to cyclicity, with an increase in the duration of cycles since 1998. It was determined that the regional incidence of influenza was significantly lower than the national average and had a tendency to decrease. The long-term influenza rate in the Rostov Region was 412.4 ± (2.045 x 131.3) (p = 0.05) or almost three times lower than that in the country 1,553.0 ± (2.045 x 301.2) (p = 0.05). The dynamics of influenza incidence in the Rostov Region also had a cyclical course with a smaller amplitude of fluctuations (3,215.1 %оо) than in the Russian Federation (5,164.8 %оо). The duration of epidemic cycles in 1990-1998 and 2002-2012 was two years but we noted a three-year cycle in 1999-2001. We established a correlation between influenza and URTI rates and population density in regional cities and various age groups: the highest URTI rates (74.9 %) were registered in children between two to 17 years of age while 52.5 % of influenza cases were adults (aged 18+). Conclusion: The established characteristics of the development of the epidemic process of influenza and URTIs in the Rostov Region prove the necessity of a differentiated approach to organizing and implementing comprehensive preventive measures within optimization of epidemiological surveillance of these diseases, and can also serve as basic criteria for disease prediction.

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