[The morbidity and immunological structure of the population in viral hepatitis A at different phases in the development of multiyear epidemic cycles]. / Zabolevaemost' i immunologicheskaia struktura naseleniia pri virusnom gepatite A v raznye fazy razvitiia mnogoletnikh épidemicheskikh tsiklov.

For the first time population immunity to virus hepatitis A has been studied during three different phases of prolonged morbidity cycles of this infection, and the results of this study have been compared with the data on morbidity in different age groups. Pronounced variability of the immunological structure of the population in different age groups, found to be related to the dynamics of hepatitis A morbidity, has been established. Fluctuations in immunity level are most pronounced among children aged 1-6 and 7-14 years, having the least proportion of seropositive persons. A new epidemic cycle is started among these groups of the population, and at the first stage this cycle is manifested by an increase in the intensity of the latently developing epidemic process. This is followed by the activation of registered morbidity among the whole of the population. Seroepidemiological study may be used both for prognostication purposes and in the system of surveillance on this infection.

[Methodological bases for the study and the patterns of the seasonality of viral hepatitis A]. / Metodicheskie osnovy izucheniia i zakonomernosti sezonnosti virusnogo gepatita A.

On the basis of the study of the data on the incidence of viral hepatitis A in one of the districts of a big city for 20 years the authors come to the conclusion on the advisability of a comparative study of the monthly changes in the incidence of hepatitis A within individual uniform morbidity cycles covering the periods of many years and the use of average monthly data for many years for plotting the typical curve, as well as the use of the simplified for the calculation of the upper limit of annual morbidity. Similarities and differences in the monthly dynamics of morbidity in the years of high and low morbidity levels have been revealed, and the age group of the population (20-39 years) which ensures the continuity of the epidemic process all the year round has been determined. The factors contributing to the seasonal activation of the epidemic process start operating in June among schoolchildren aged 11-14 years, and later their operation spreads to other groups of the population.

[Structural changes in influenza virus RNA during its attenuation]. / Strukturnye izmeneniia RNK virusa grippa v protsesse ego atteniuatsii.

Changes in structures of only two genes of influenza virus--M and NS genes were found during virus attenuation by the method of oligonucleotide mapping. Such changes were observed in virulent and attenuated viruses (passages 10-23 in chick embryos) by comparing intermediate variants of the virus (passages 11-16 in chick embryos). These results allow us to conclude the important role of these genes in virus attenuation and in connection with virulence of the virus.