Evaluation and predictive methods of epidemical situation in the area of acute enteric infections

Abstract

Introduction.  Despite the fact, that nowadays acute intestinal infections (AII) sick rate is decreasing, the aggravation of the epidemical situation is always there. Increased attention to AII caused by unpredictable epidemical rises of the AII diseases, which cannot be prevented without assessing the epidemical situation of these infections and forecasting of the levels of sick rate. However, developed mathematical methods of forecasting in most cases do not take into account the risk factors, also they are time-consuming and it is difficult to calculate them; and developed special computer programs, which predict infectious sick rates, are often in the lack in the institutions of sanitary-epidemiological service. An urgent problem for today is establishing of the most influential social and environmental factors, which can make a contribution to the spread of AII. The aim of this work was to improve the method of assessment and prediction of epidemic situation of AII by identifying the influence of climatic and demographic factors.  Materials and methods. In order to determine the influence of meteorological and demographic factors on the epidemic process of acute intestinal infections the official reports of the State Sanitary and Epidemiological Service of Ukraine in Sumy region, the Department of Statistics, Sumy Regional Center for Hydrometeorology and  Environmental Monitoring have been studied.   Results and discussion.   The work on the evaluation of the epidemiological situation of the AII begins from collecting data, according to the AII sick rate. The main source of this information is the logbook of infectious diseases, which recorded all sick people that were found in the area. It is necessary to gather the initial information, calculate the sick rate and monthly distribution of AII cases on investigated area and evaluate the tendency.  At the same time with accounting of AII cases on investigated territory, takes place a monitoring of air temperature, humidity and rainfall. Simultaneously, should be gathered the information about the population on the investigated area, its density (for 1 km²), natural and migratory movement. When the information is gathered, begins the stage of analytical research. At first, determines the long-term tendency of the sick rate. If the average time of growth of the sick rate ranges from 0 to 1.0% - the epidemiological situation of this nosology is good, ranges from 1.1% to 5.0% - unstable, more than 5.0 % - bad. The probability of the influence of natural and social "risk factors» (X) on the AII sick rate (Y) calculates according to this formula: R_xy = Ʃ d_x•d_y  / √Ʃ d_x²•d_y², where R_xy - correlation coefficient; d_x - departure from the arithmetical average of  levels of natural or social factors; d_y - departure from the arithmetical average of the annual sick rate or seasonal distribution.        If it was founded an authentic correlation  (p<0.05) between the average monthly rates of air temperature, humidity, rainfallы, number and density of population (per 1 km²), natural and migratory movements, and the sick rate of the AII nosological entities, the AII epidemical situation, in a case of increasing of the indicators of abovementioned "risk factors", will be also considered as unstable, which requires immediate elaboration and implementation of the targeted preventive steps. a result, the study found, that in current conditions in Sumy region the epidemical situation of shigellosis, AIIDA and AIIUE is good, according to Т_red.^av.= -10.7 % for shigellosis, and  Т_gr.^av. = +0.6 % for acute intestinal infection, caused by other determined agents (AIIDA) and acute intestinal infections of unknown etiology (AIIUE); epidemical situation of salmonellosis is unstable, because: Т_gr.^av.= +2.3 %. It was found, that the number and density of population (1 km²). Similar relationships were also found between the levels of salmonellosis sick rate and net migration rate  and natural population movement. On the seasonal distribution of salmonellosis sick rate affected temperature and rainfall. From the average daily temperature levels, to some extent, depended a frequency of cases, in which people with AIIDA asked for medical service. Thus, despite the fact, that in the current conditions of Sumy region, epidemical situation of shigellosis and AIIDA is considered as good, accordingly: Т _red.av.= -10.7 % і Т_gr.av .= +0.6 %, increasing of number and density of population and average daily temperature in this region can cause increase the sick rates of shigellosis and acute intestinal infection, caused by other determined agents. The epidemical situation of salmonellosis at the time of research was unstable (T _gr.av. = 2.3 %), but if the indicators of the natural and migratory movement of population are increasing, the situation will be worse. Although, climatic factors haven`t got a direct relation to the transmission of salmonellosis agents, and not directly related to it, but they influence on the dynamics of this disease. Conclusion. So, in a case of growth of number and density of population, can exist the favourable conditions for increasing of shigellosis epidemical process; rising of natural and migratory movements and levels of daily average temperature and rainfall promote the probability of salmonellosis; rising of environmental temperature promotes the probability of AIIDA. To avoid the aggravation of the AII epidemical situation, when the levels of natural and social "risk factors" are growing up, it is necessary to organize and take the prophylactic measures immediately. This method can be used by Hygienic and Epidemiological Center in conducting of epidemiological surveillances of intestinal infections for optimizing of preventive measures.