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.     

Epidemiology of bacillary dysentery in Algeria. II. The seasonality of dysentery

Morbidity rises during the period of summer and autumn are characteristic of bacterial dysentery in Algeria. During the last 18 years no essential changes in the seasonal character of bacterial dysentery were observed in the country taken as a whole. However, in different climatic and geographical zones of the country the seasonal character of dysentery greatly varies from one zone to another and essentially differs from the seasonal character of dysentery morbidity, typical of the country as a whole for many years. The most pronounced manifestations of seasonal rises are observed in the Sahara zone. The seasonal character of dysentery is formed mainly by morbidity among patients belonging to 3 age groups. The seasonal rises of dysentery can be probably explained by the complex of social and climatic factors, as well as by the biological features of the causative agents of this disease.     

Etiologic structure of bacterial dysentery in the USSR in 1983-1985

The etiological structure of dysentery in the USSR in 1983-1985 is characterized. Sonne dysentery was found to prevail in the territories with adequate water supply, while dysentery caused by Shigella flexneri prevailed at the territories with unsatisfactory water supply. S. dysenteriae and S. boydii were found to play a limited role in the etiology of dysentery. In the presence of global pandemic, an increase in the isolation rate of S. dysenteriae I in the USSR is observed. The data on the biochemical structure of S. sonnei are presented.     

Relation of the epidemiological characteristics of dysentery to the biological properties of the causative agents

The main forms of the epidemic manifestation of dysentery induced by different causative agents in 1975-1980 were revealed. During these years the cases of dysentery induced by Shigella sonnei, biovar II, were found to prevail (82.0-90.1%) both at the periods between epidemics and at the periods of the seasonal rise of morbidity. The experimental infection of white mice by intraperitoneal inoculation revealed no relationship between the seasonal rise of morbidity in dysentery and the virulence of its causative agents.     

The epidemiological characteristics of meningococcal infection in the USSR

The epidemiological analysis of morbidity in meningococcal infection in the USSR in the period of 1969-1987 showed that the second rise of the morbidity level occurred in 1984 and was followed by its decrease in most of the regions of the USSR. This study also revealed that the characteristic feature of the second rise of morbidity in meningococcal infection was a considerable involvement of young children (aged up to 3 years), as well as the increased etiological role of group B meningococci in cases of meningococcal infection and the circulation of these microorganisms among the population. Besides, the preservation of the etiological importance of group A meningococci in many regions of the USSR, especially among adults, was noted. In this connection, the use of Soviet group A meningococcal polysaccharide vaccine on epidemiological indications was considered to be epidemiologically substantiated.     

Influenza epidemics in the USSR and Czechoslovakia in 1979-1984

In this work materials characterizing the appearance and development of influenza epidemic at the territories of the USSR and the Czech Socialist Republic are presented, the common features and differences of the epidemic process in both countries are recorded. The work shows that in both countries the appearance of this epidemic is caused by the same virus. In most cases the epidemic started earlier and lasted longer in the USSR, but morbidity rate during the epidemic was, on the whole, higher in the Czech Socialist Republic. Similarity in the course of the primary period of the epidemic processes from their appearance to their maximum rise was observed. In both countries the maximum rise of morbidity rate was registered on weeks 3-4 from the beginning of the epidemic.     

Analysis of the seasonality of acute intestinal diseases with regard to the detection of dysentery by antigen indication

Coincidence in the seasonal changes of the registered morbidity in dysentery and in other acute intestinal diseases is observed. The occurrence of Shigella antigens, detected with the use of erythrocyte diagnostic reagents, in the excreta of patients with the clinical diagnosis of dysentery and patients with other acute intestinal disease has a seasonal character, its peak coinciding with the period of increased morbidity in bacteriologically confirmed dysentery. The correction of monthly morbidity levels in dysentery and in other acute intestinal diseases with due regard for the proportion of Shigella antigens in the findings, made in the groups of patients with the clinical diagnosis of dysentery and with the diagnosis of other acute intestinal diseases for the corresponding month, has revealed that the actual morbidity in other acute intestinal diseases has a less pronounced seasonal character in comparison with the registered morbidity. This fact substantiates the statement that in the group of patients with other acute intestinal diseases a large proportion of such diseases is, actually, of a noninfectious nature.     

The cyclicity and prognosis of shigellosis morbidity in Russia

The epidemic process (EP) of shigellosis morbidity proceeds in cycles. As shown in this study, cyclic curves are the sum of polyharmonic fluctuations, being the axis of EP. The duration of one cycle is 18 years, and its configuration is stably retained for a long time. In Nizhny Novgorod shigellosis morbidity is strongly correlated with air temperature is summer at the peak of cyclic rises and moderately correlated in the years of low morbidity. In some cities of the Russian Federation fluctuations of air temperature have been found of occur synchronously with disturbances of the magnetic field of the earth. The character and stability of EP cycles provide grounds for the prognostication of shigellosis morbidity. The current cycle will end in the year 2000, and then natural preconditions for a new cyclic rise will appear.     

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.     

The etiological structure of shigellosis in the USSR in recent years

The characterization of etiological structure of Shigella infection in the whole of the USSR, in individual union republics and at a number of other administrative territories of the USSR in recent years is presented. S. flexneri has been shown to prevail at the territories with unsatisfactory water supply of the population, and S. sonnei prevails at the territories with good water supply. At the former territories S. dysenteriae and S. boydii retain their etiological importance, while at the latter ones their role is insignificant. At a number of territories the infectious process has stopped: no isolation of these shigellae from dysentery patients and carriers is observed any longer. Among the causative agents of Flexner's dysentery, S. flexneri 2a, 6 and 1b (in different combinations) play the leading role.     

Current methods of intraspecies typing of Shigella sonnei. 3. Bacteriophage typing]

Data are presented concerning the study of the phage type of Sh. sonnei isolated in various regions of the USSR. The strains isolated belonged to 64 phage types corresponding to the Hammarstr?m's scheme. A variety of Shigella sonnei phage types both in one and in different territories of the country provided future prospects for successful use of phage typing for the purpose of epidemiological supervision and analysis of dysentery morbidity.     

Epidemiological analysis of hepatitis A morbidity

A retrospective epidemiological analysis of hepatitis A morbidity for many years among the population of two neighboring towns in the temperate climatic zone of the USSR has revealed the cyclic character of the epidemic process without a perceptible decrease in its extensiveness and has determined the high-risk groups, as well as the beginning of the seasonal rise of morbidity in these groups. The results of the study indicate that different levels of hepatitis A morbidity and risk groups can be observed in these two neighboring towns. At periods of a lower morbidity level the high-risk group embraces schoolchildren, and when morbidity is at a higher level the risk group includes schoolchildren and preschool children in organized groups. Among the latter the morbidity level is influenced by factors acting all the year round and among school children, by seasonal factors. The beginning of the seasonal rise of morbidity falls on August, while in organized groups of children of preschool age the seasonal rise of hepatitis A morbidity begins 1-1.5 months later. All prophylactic measures for controlling hepatitis A should be carried out with due regard to these features of the epidemic process.     

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.     

Dynamics of typhoid-paratyphoid infection morbidity in Chimkent Province

The study of the time course of typhoid-paratyphoid infections in the Chimkent region for the period of 1944-1979 has revealed the periodicity of their rises (falls) repeating every 2-4 years. Since 1964 the tendency towards the decrease of morbidity has been observed. The annual rate of this decrease is 4.9%. Periodic changes in the annual level of typhoid-paratyphoid infections do not depend on the temperature of the air and the seasonal number of winged flies. There is a pronounced direct correlation between the annual morbidity level and the frequency of summer precipitations, this correlation being more pronounced during the first 2 summer months.     

Seeding efficiency of the causative agent of dysentery as an index of the intensity of the epidemiologic process]

A study was made of the character and extent of interrelationship between the indices of dysentery morbidity and the indices of the seeding efficiency of dysentery bacilli persons who did not apply for medical aid. Establishment of such interrelationship permitted the authors to suggest the use of a more objective index of the seeding efficiency of dysentery bacilli, along with morbidity indices, for the assessment of the intensity of the epidemic process in this infection. On the basis of investigations carried out the authors came to the conclusion that a tendency to the increase of dysentery incidence the last few years chiefly bore a "statistical" character and was due to the improved detection of patients and carriers.     

The importance of Shigella boydii in shigellosis morbidity in the USSR

The etiological role of S. boydii in Shigella infections registered at different territories of the USSR in 1986-1987 was analyzed. As established by this analysis, S. boydii infection occurred mainly at the territories with unsatisfactory water supply of the population; from these territories the infection spread to ther territories of the USSR. The dominating serovars causing S. boydii dysentery, as well as Shigella infections, at different territories of the USSR was shown to be identical, which was indicative of the fact that the immunological factor had no influence on the etiological structure of Shigella infections, determined by the activity of the main routes of the transfer of infection. On the whole, S. boydii serovars 2, 4 and 1 were found to prevail in the USSR.     

The etiological structure of shigellosis in the former USSR--an indicator of the activity of the main routes of infection transmission]

The data on the etiological structure of Shigella infections in the USSR in 1988-1989 are presented. The study showed the dominating role of S. flexneri with S. sonnei also retaining great importance in Shigella infections. The process of the liquidation of S. dysenteriae and S. boydii infections began in some large cities. The domination of dysentery caused by S. flexneri and a high typhoid rate, particularly in Central Asia, were due to poor water supply of the population. The spread of dysentery caused by S. sonnei was completely independent of the water factor. The decisive role in the transmission of S. sonnei in infective doses was explained by decentralized milk supply.     

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.     

Epidemiology of bacillary dysentery in Algeria. I. The epidemiological aspects of dysentery in Algeria

Bacterial dysentery plays an important role among infectious diseases in Algeria. A tendency to the growth of the morbidity rate has been observed. Dysentery is irregularly spread in different zones of the country. The highest morbidity rate is registered in the Sahara zone and in the eastern part of the country. The morbidity rate among the urban population is higher than among the rural population. S. flexneri prevail in the etiological structure of dysentery infection. Of all age groups, the highest morbidity rate is observed among children during the first 2 years of life. In recent years lethality varies between 2.9% and 7.5%. Patients are hospitalized mainly on the basis of clinical symptoms.     

Relation entre habitat et peuplements de poissons: Essai de definition d'une methode numerique pour des rivieres nordiques

Estimates of primary production in relation to bacterioplankton growth kinetics have been made in three fish ponds with mono and polyculture in the Fish Farm Nivka, Kiev, USSR. Since the basic process of primary production is dependent upon such prevailing conditions as temperature, light and nutrient rather than upon the introduction of fish species, almost similar production rates were obtained in these ponds, with the variance ratio found not significantly different from zero (P > 0.05). So was the case with bacterioplankton growth kinetics (P > 0.05). A maximal gross production coupled with a bacterioplankton peak was demonstrated in the summer month of July with the rise of temperature of the water, while minimal production was observed in September. The effect of season was highly significant (P < 0.001) upon both primary production and bacterioplankton. Extreme deficiency of the net photosynthetic production of O₂ was observed in summer due to less prevalence of phytoplanktonic algae as a consequence of heavy grazing by the herbivorous fishes at the time of their active growth. A plot of biochemical oxygen demand as function of the respiratory loss of O₂ due t0 bacterial population showed a direct linear relationship (P < 0.001). Lack of definite correlation (P > 0.05) was indicated between the BOD and the total bacterioplankton population. There existed no definite relationship (P > 0.05) between primary production and bacterioplankton, perhaps because of the very low percentage of autotrophic photosynthetic bacteria and abundance of heterotrophic bacteria in the composition of total bacterioplankton.