[Methodological bases for the study and the patterns of the seasonality of viral hepatitis 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.