Population migrations and the epidemic process of Flexner and Sonne dysentery

Analysis of the materials from the Khabarovsk Territory for the representative period of 25 years (1956-1980) revealed the influence of the migration of the population on the level and dynamics of morbidity in different kinds of dysentery, Flexner's dysentery shown to occur more frequently than Sonne dysentery. Intensive migrations increase the proportion of susceptible persons among the population, thus facilitating the formation and circulation of Shigella strains with pronounced virulence.     

Characteristics and trends in the development of an epidemic process of Sonne and Flexner dysentery among preschool children

The results of studies indicate that the morbidity rates of dysentery among children attending preschool institutions and children brought up at home converged in recent years. This phenomenon was most pronounced among children of the kindergarten age group. At the same time dysentery caused by Sh. sonnei and Sh. flexnery produced a higher morbidity rate among children attending nursery in comparison with that among children of the same age group brought up at home. Group infections in preschool institutions were caused by Sh. sonnei in 89.1% of cases and by Sh. flexneri in 10.9% of cases. Outbreaks due to the transfer of infection through everyday contacts were observed only in dysentery caused by Sh. sonnei, constituting 71.4% of the total number of dysentery outbreaks.     

Patterns determining the dynamics of the epidemic process in Sonne dysentery and its relation to the type of causative agent]

The results of studying the dynamics of the epidemic process of dysentery, based on the data from 3 districts of Moscow, are presented. The study revealed the periodicity of 3 years in the course of the epidemic process of dysentery, occurring against the background of a considerable predominance of Sh. sonnei, biochemical type 2. The use of the cohort method for analyzing the age structure of dysentery cases showed the possibility of using this method to find out to what extent the epidemic process repeatedly affected the same groups of population.     

Tendencies in the epidemic process of dysentery in Ryazan

In shigellosis caused by Sh. sonnei and Sh. flexneri the epidemic process was found to have considerable difference in the tendencies and pace of its development. Shigellosis which dominated in the etiological structure at the period following 1966 was dysentery caused by Sh. sonnei; it showed the tendency towards a decrease in morbidity rate. Dysentery caused by Sh. flexneri was second in respect to the frequency of its occurrence after 1966 and showed the tendency towards increase. The simultaneous circulation of Sh. sonnei and Sh. flexneri, the differences in the epidemiology of these types of shigellosis make it imperative that they be studied separately, taking into ccount their etiological selectivity to the main routes of transmitting the infection.     

An analysis of the dysentery epidemic process in Blagoveshchensk

The retrospective analysis of dysentery morbidity in Blagoveshchensk for the period of 1960-1987 was made. The regularities linking general natural and biological factors triggering the epidemic process with dysentery morbidity among the population are emphasized. The study revealed that under the conditions of Blagoveshchensk dairy products were of major epidemic importance among factors contributing to the transmission of dysentery. Such a factor as flies also had a definite influence on the epidemic process of dysentery. Another risk factor was drinking water which influenced the epidemic process both directly and indirectly through dairy products and, probably, other foodstuffs. Reliable correlation between dysentery morbidity among the population and the quality of dairy products, tap water and the number of flies was established.     

Natural population migration and the dysentery epidemic process

The complex analysis of materials obtained in different regions and territories of the Far East makes it possible to establish that the natural migration of population affects dysentery morbidity by enhancing the susceptibility of human population to this infection. The internal mechanisms of the influence exerted on morbidity by the natural migration of population is disclosed from the viewpoint of the theory of the self regulation of the epidemic process.     

Manifestations of the cyclic nature of the epidemic process in dysentery

Different forms of dysentery, especially those caused by Sh. sonnei and Sh. flexneri, have been found to differ considerably in their cyclic recurrence. The development cycles of the epidemic processes of dysentery have an objective character, occur in the presence of any tendencies in the morbidity rate, and depend on the natural factors. Thus, the cycles of increase and decrease in morbidity are 3, 6, 9, 12 years for dysentery caused by Sh. sonnei and 6, 7, 8 years for dysentery caused by Sh. flexneri.     

Duration of bacterial discharge in Sonne dysentery]

The authors report on the results of their observations during 3 epidemic outbreaks. Despite different intervals at which the bacteriological examinations were carried out comparable data were obtained: during 2 outbreaks when no chemotherapeutic agents were used in 78.0 and 79.9% of children shigella discharge ceased in 4 weeks. Daily bacteriological examinations carried out in the course of the 3rd outbreak showed the maximal intermittent bacterial discharge for up to 79 days in individual cases.     

Formation of the dysentery epidemic process in three small towns]

Data are presented concerning the epidemiological analysis of Sonnei dysentery outbreaks in three towns connected by common nutrition and water supply. The epidemic processes in these populated localites were strongly interrelated. Possibilities of the effect of the water factor on the extent of Sonnei dysentery incidence were studied as well. The results of studies led to the conclusion on the presence of numerous action forms of the water factor which should be taken into consideration in carrying out prophylactic and antiepidemic measures in Sonnei dysentery.     

Nature of the epidemic process in Sonne and Flexner dysenteries and the causes of its induction

A comparative study of the epidemic process in Sh. sonnei and Sh. flexneri dysentery in different regions of the USSR revealed that the morbidity level of Sh. sonnei dysentery changed simultaneously in the regions under study at intervals of 2-3 years. Sh. flexneri dysentery showed morbidity rises occurring at intervals 6-8 years, and their occurrence did not coincide with the periods of elevated morbidity in Sh. sonnei dysentery. The data obtained in the cohort analysis and in the study of recurrent morbidity suggest that Sh. flexneri dysentery produces more pronounced postinfection immunity than Sh. sonnei dysentery, and the immunological factor probably affects the dynamics of the epidemic of these Shigella infections.     

The possibility of using the demonstration of Shigella antigens in the study of the epidemic process in dysentery

The detection of Shigella antigens in feces in accordance with the results of the passive hemagglutination test is more effective than the bacteriological method for finding out persons infected with Shigella, especially in the absence of pronounced clinical manifestations of dysentery, and can be used in the study of the mechanism of the epidemic process. The examination of two groups, each consisting of permanent and temporary members, has revealed that the use of this method for detection of the antigen makes it possible to perform the epidemiological analysis of morbidity and, in particular, to determine the source(s) of infection.