FEATURES OF EPIDEMIC PROCESS OF INFLUENZA A(H1N1)PDM09 AND A(H3N2) IN RUSSIA FROM 2009 TO 2017.

The goal of this work is to compare the key parameters of influenza epidemics of different etiology. Four epidemics of influenza with predominance of influenza A(H1N1)pdm09 and 4 epidemics of influenza A(H3N2) were analyzed using the database of the Federal State Research Institute of Influenza on morbidity, hospitalization, deaths from influenza in 59 cities in the period from 2009 to 2017. The intensity of epidemics involving the influenza A(H1N1)pdm09 decreased from high to medium, while the intensity of epidemics of influenza A(H3N2) increased from low to medium. In the epidemic of influenza A(H1N1)pdm09 in the total population, the incidence of influenza and ARI decreased by a factor of 1.6, while the mortality among patients decreased by a factor of 1.7 in all age groups, except for those over 65 years, for whom the incidence and mortality increased by factors of 1.4 of 2.3, respectively. In the epidemic of A(H3N2), a trend for increasing morbidity and mortality was more pronounced among individuals older than 65 years. Pandemic influenza remains the leading cause of deaths. Among the dead in the epidemic of influenza A(H1N1)pdm09, the proportion of young individuals decreased (including a fourfold decrease of lethality in pregnant women), while the proportion of persons over 65 years increased 7.8 times; in the epidemic of influenza A(H3N2) only 2.5-fold increase was observed. In the epidemic of influenza A(H1N1)pdm09, the proportion of lethality increased among people with cardiovascular diseases and diseases of the internal organs; in the epidemic of influenza A(H3N2), the proportion of lethality increased among people with immunodeficiency, diseases of the internal organs and respiratory system.

[Comparison of the influenza epidemics in Russia caused by the pandemic virus A(H1N1)pdm09 within the period from 2009 to 2013].

Comparative analysis of the three past epidemics with the participation of the pandemic influenza A(H1N1)pdm09 was conducted according to the results of the epidemiological trials of two WHO National influenza centers for the morbidity, hospitalization, and mortality of the influenza in 59 cities of Russia for the period from 2009 to 2013. The first wave of the pandemic of 2009 was the most severe. Compared with this wave, during the next epidemics of 2011 and 2013, the involvement of urban population in the epidemic was reduced, as well as the morbidity in the people 15-64 years old and schoolchildren 7-14 years old. The duration of the epidemic among the adult population, the mortality rate of the total population, and the mortality rates in all age groups were also decreased. Vice versa, the incidence in the children of preschool age and the elderly people and the duration of the epidemic among children (especially preschool children) were increased. The share of patients 65 years and older, children 0-2 years old, and patients with pathology of the cardiovascular systems among the deceased patients increased to 33.6%.

[An influenza pandemic in Russia as a part of a global spread of the influenza A(H1N1)pdm09 in 2009-2011].

The comparison of the first and second waves of the pandemic influenza A(H1N1)pdm09 in the world and Russia was performed on the basis of weekly reports of Regional offices for Europe and on the data of the Federal Center for Influenza on a weekly incidence of influenza and acute respiratory viral infections, hospitalization, and mortality from the influenza in the age groups of population in 49 cities of the Russian Federation. The first wave of the pandemic, which continued in the countries of the world all summer, was of mixed etiology and, in spite of the availability of imported cases, has not caused a steep increase in Russia. The second wave of the pandemic in the countries of the Southern hemisphere was less intense. In the countries of the Northern hemisphere (in autumn 2009), on the contrary, it was more intensive, which was associated with different seasonality of influenza in these hemispheres. In Russia, the second wave (2011) was of a lesser intensity as compared to the first with respect to the duration in the country and in urban areas, the incidence in the entire population, including schoolchildren and adults, the rate of hospitalization and case fatality rate reduction of laboratory-confirmed influenza infection. The duration of the last pandemic of 2009 was the same as in 1957 and 1968, and longer than in 1977. The morbidity was one-half less than in the pandemic of 1957 and 1968, and was approaching the pandemic 1977. At the same time, the incidence in children 3-6 and 7-14 years was higher than in previous pandemics.

Comparison of influenza outbreaks in the Republic of Kazakhstan and Russia induced by 2009 yearly new variant of A(H1N1) influenza virus.

The aim of the work is the comparison of the epidemiology of influenza and acute respiratory virus infections (ARVI) in the Republic of Kazakhstan with the corresponding influenza epidemic in Russia induced by influenza pandemic virus A/California/07/2009 in 2009. Data on influenza and ARVI from the Republic of Kazakhstan and Federal Center of influenza was collected and investigated over the course of several weeks from hospitalized patients with the same diagnosis among all population and in age groups on 16 territories of Kazakhstan and in 49 major cities of Russia. The epidemic in Kazakhstan resembled the Russian epidemic in terms of its abnormally early beginning, expression of monoaetiology, the spread of the epidemic into all territories and start of the epidemics among adult population. High percentage of hospitalized people and lethal outcome were registered in this epidemic. Similarity of epidemic process character in corresponding border-line territories of both countries was found out.

[Epidemiology of influenza A/California/07/09 (H1N1) in population of 49 cities in Russia in 2009 - 2010].

AIM: Comparison of influenza A(H1N1) epidemic in Russia caused by pandemic virus A/ California/07/09 (H1N1) in 2009 with previous epidemics of influenza A of this subtype. MATERIALS AND METHODS: Analysis of A/California/07/09 (H1N1) epidemic was carried out in 49 cities--bases of Federal center of influenza. Parameters of this epidemic by duration, influenza and acute respiratory viral illness morbidity, hospitalization and mortality rates from laboratory confirmed influenza in the population in general and in age groups (0 - 2 years, 3 - 6 years, 7 - 14 years, 15 - 64 years, 65 years and older) were studied. RESULTS: A/California/07/09 (H1N1) epidemic differed from the seasonal epidemics by unusually early onset, monoetiology, wide coverage of the population of cities, longer duration and higher morbidity in the population from 7 to 64 years of age, higher rate of hospitalizations and number of lethal outcomes in the population from 15 to 64 years of age. Lower morbidity, rate of hospitalizations and number of lethal outcomes was notable in individuals older than 65 years, that is an indication of the presence of an anamnestic immunity. CONCLUSION: Comparative analysis of A/ California/07/09 (H1N1) epidemic with 3 previous influenza pandemics in Russia has shown, that during this epidemic population morbidity was 2 times lower than during 1957 and 1968 pandemics, and the rate approached that of the 1977 pandemic. This epidemic differed from previous pandemics by a delay of city-megapolis and preschool aged children involvement, early onset and lower intensity of peak; lower relative rate of morbidity among adult population and higher--among school children; higher multiplicity of excessive morbidity of children compared with morbidity of people older than 15 years.