EPIDEMIC PROCESS

From Big Medical Encyclopedia

EPIDEMYCHESKY PROCESS (the Greek epidemos extended among the people) — the process of spread of infectious diseases in human society consisting in formation of a chain of the epidemic centers which are consistently arising one of another. Epidemic process is the main object studied by epidemiology (see).

AA. the item arises and in the subsequent is supported only at existence and interaction of three factors (elements, links): a source of a contagium (the sick person or an animal, the person or an animal — the carrier of the activator); the ways and factors providing transfer of a contagium from the infected organism healthy (e.g., water, foodstuff, household items, blood-sicking arthropods); susceptibilities of the population to this infection (see the Invasion, the Infection). Providing continuous change of generation of the activator, AA. the item causes existence of the activator as look.

However these, though the main, factors E. items in itself are not E yet. item, its motive powers. Motive powers they become only when their interaction joins social also an environment, more precisely, when this interaction is mediated corresponding social and an environment, to-rye in different combinations can stimulate or oppress development E. item.

The natural factor is quite often connected with a natural ochagovost (see). E.g., the person can catch a tularemia (see) or a tick-borne encephalitis (see a tick-borne Encephalitis) only in territories where animals — sources of these infections and blood-sicking parasites — carriers of their activators live. Visible effect of a natural factor on E. the item at other infectious diseases. So, during the autumn and winter period against the background of reduction of activity of solar radiation processes of self-cleaning of the environment from causative agents of acute intestinal infections are sharply slowed down, and during the spring and summer period melt and rain waters promote washout of sewage in open reservoirs that at non-compliance a dignity. norms and rules of water use can lead to increase in frequency of cases of infection, napr, a typhoid (see).

The defining influence on E. items render social conditions, such as the nature of economic activity and material security of the population, the nature of communication of people, population density, level of improvement of settlements, a working condition and life, sanitary and hygienic skills, means of communication, mass movements of people, wars, hunger, a condition of health care. E.g., rational water supply (see), the sewerage (see) and cleaning of the inhabited places (see) at observance by the population dignity. - a gigabyte. norms and rules are capable to reduce incidence of intestinal infections considerably. Huge influence on character and intensity E. items at many earlier eurysynusic infectious diseases render the actions directed to creation of the fullest immune layer among the population i.e. impact on the third factor E. the item — a susceptibility. In our country immunoprevention is firmly regulated, there is a calendar of preventive inoculations (see Immunization, t. 25, additional materials) thanks to what incidence of diphtheria (see), whooping cough (see), to a bark (see), poliomyelitis sharply decreased (see) and many other infectious diseases. Experience of the USSR in performing the mass immunoprevention which provided, in particular, elimination of incidence of natural smallpox in our country by 1936 was used by WHO at the organization of the program of eradication of smallpox on the scale of the globe that came to the end with a clear victory over this terrible inf. a disease (see Smallpox natural).

Intensity of development E. the item in many respects is defined by the properties of a disease-producing factor causing duration of an incubation interval (see), specifics of a pathogeny, frequency of emergence of various forms of display of an infection (see. Infectious diseases, Parasitic diseases) — acute, chronic, carriages [see the Carriage of contagiums (invasion)], and also the mechanism of transfer of the activator (see the Mechanism of transmission of infection). So, at a number of diseases the incubation interval is estimated for hours, napr, at food toxicoinfections (see Toxicoinfections food), or for 2 — 3 days, napr, at flu (see), at others — it lasts up to several years, napr, at a leprosy (see). It, naturally, influences the frequency of emergence of the subsequent cases of infection and, therefore, the quantitative characteristic of a current E. the item in time. Sharply proceeding infections are characterized by the short infectious period, napr, flu, measles, cholera, etc. whereas at a number of chronically proceeding infectious diseases, napr, chronic dysentery, an amebiasis, tuberculosis, etc., the patient remains a long time a source of an infection (see). The ratio of «healthy» carriers and patients with clinically expressed disease also influences development E. item.

Infections, activators to-rykh are transmitted in the airborne way, extend most quickly, affecting often (as, e.g., flu) for short term in many countries and continents the mass of the people susceptible to them. At the diseases which are characterized by the fekalnooralny mechanism of transfer of the activator, AA. the item usually proceeds less intensively. However in the presence of a large number of sources of an infection or massive pollution of water or foodstuff a disease-producing factor emergence of large epidemics of the intestinal infections extending to considerable territories is possible.

Intensity E. the item is characterized by incidence and depending on the frequency of cases of this or that inf. diseases in this area for a certain span epidemic (see) or a pandemic is estimated as sporadic incidence (see), (see) . The term an endemia (see) is not connected with intensity

E. the item, and designates constant existence in this area of diseases of people of a certain disease. At separate inf. diseases intensity E. items and its dynamics with characteristic alternation of rises and recessions of incidence as within one calendar year (the phenomenon of seasonality), and at an interval of several years (the phenomenon of frequency) are rather typical. Also involvement in E is not less characteristic. the item of these or those preferential struck age and professional groups of the population.

The doctrine about E. the item, being fundamentals of epidemiology (see), it develops constantly and improved. In a crust, time the considerable attention is paid to studying of patterns of spread of the infectious diseases caused by opportunistic microorganisms (see) and slow viral infections (see).

By the main methods of studying E. items are epidemiol. observation and experiment. At assessment E. items use a row generalized epidemiol. indicators: intensive

indicators (incidence, a lethality, mortality) characterizing extent of development E. the item from the quantitative party; extensive indicators — distribution of all studied phenomenon on separate groups according to this or that sign: e.g., division of all considered cases of a typhoid into three groups depending on a factor of transfer of a disease-producing factor (water, foodstuff, objects of use), distribution of patients on weight of disease.

The main indicator characterizing intensity of a current E. the item, is incidence (see). This indicator is used for assessment of level and the nature of distribution of cases of diseases within the studied territory, for determination of frequency of developing of a disease in different age and professional groups of the population. Along with it in the analysis E. items use indicators of an ochagovost and weight a wedge, diseases, data on sources and ways of spread of an infection (see. Epidemiological indexes). For definition of the phenomena of seasonality and frequency indicators of incidence study in dynamics — on months within one calendar year or by years within several years. During the studying of action of any anti-epidemic factor, napr, influences of preventive immunization (see) on intensity E. items, compare indicators of incidence in equal on quantitative, age and to other characteristics groups of the population subjected to immunization and neimmunizirovanny.

282 EPIDEMIC CEREBROSPINAL MENINGITIS


in the domestic literature devoted to epidemiology are discussed Recently the provision on self-control E. item. At the same time E. items actually consider as biol. the phenomenon also, therefore, assimilates to epizootic process. It is not excluded that at the beginning of development of humanity mechanisms of self-control E. items were similar to those, to-rye are observed at development of an epizooty in population of animals. However in process of social and economic transformations about-va E. the item gained consistently increasing social character along with what value of mechanisms of its natural regulation so consistently decreased. It is historically obvious that intensity of impact of social factor on patterns of distribution of various antroponoz, i.e. on E. the item, so, and on mechanisms of its regulation, consistently increased in process of transition from one socio-historical formation to another. So, during transition from a feudal system to capitalist against the background of universal rapid development uncomfortable in a dignity. - a gigabyte. the relation of large settlements, mass migration of the population and development of international trade constantly there were devastating epidemics not only the antroponoz which are transferred in the airborne way (e.g., natural smallpox), but also infections with more difficult (fecal and oral or transmissible) the mechanism of transfer (e.g., belly and sypny typhus). Practically these epidemics faded only with considerable reduction of number of people, susceptible to this infection, owing to their death or transferring of a disease.

In the subsequent public actions for accumulation of efficiency of a complex of sanitary and preventive measures, thanking the Crimea sharply decreased or activity of ways and factors of transfer of activators of a number of infectious diseases was completely excluded and immunity of the population to many of them is provided, actually replaced self-control E. item. Example of radical impact on mechanisms of regulation E. the item at natural smallpox is elimination of its activator as look on the scale of all planet, reached by means of rational immunoprevention. Ability about-va to liquidate an infectious disease — an additional argument in favor of the fact that E. the item at antroponoza it is deep sotsialen in essence.

Bibliography: See bibliogr. to St. Epidemiology. P. N. Burgasov, A. A. Sumarokov.

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