PANDEMIC

PANDEMIC (from Greek pan- all, whole and demos- people), the highest degree of development of an epidemic. In the precise sense of the word and its accepted usage, P. refers to such a degree of spread of an infectious disease that is expressed in an extremely wide ('universal') coverage of the entire population of a particular area. However, in many cases, the concept under consideration is used to characterize such epidemic conditions in which several or many countries are simultaneously or sequentially affected by one or another infectious disease, even if in each country the victims of the infection constitute a relatively small part of the entire population. Even more often, the concept of P. is used not in its direct sense, i.e., not to define the state of universal morbidity of the entire population, but only to characterize the state of particularly strong, unusual for a given locality, epidemic spread of one or another infectious disease. Taking into account that in the conditions of human society the movement of an epidemic is determined mainly by moments of social order (different degrees of protection against infections of various classes in a class society, disappearance or decrease in morbidity for a number of infections as a result of social preventive measures or depending on the level of development of sanitary technology, etc.), it must be recognized that in modern conditions to encounter the pandemic spread of infections, understanding it in the literal sense of the word, happens relatively rarely. This primarily includes P. of influenza (see Grip), which in the history of humanity in recent centuries manifest in the form of mass outbreaks and which can practically be considered as universal morbidity of the entire population of the globe within a short period of time (1½-2 years). The last such P. of influenza took place in 1918-19 (see Grip). To some extent, examples of the pandemic spread of infections in the literal sense of the word, some consider many chronic contagious diseases and conditions in which specific living conditions and other social factors, in the presence of a constant source of infection in the form of a chronic patient, determine the tendency of this group of diseases to universally cover a certain group of the population or residents of a particular area. From this point of view, one can include, for example, household syphilis, trachoma, tbc, malaria, helminthic diseases, etc. If the fight against pandemic influenza as a droplet infection transmitted through the air presents special difficulties, then for the group of chronic infections mentioned above, we can only speak of a tendency, since here the pandemic coverage of the population takes place only insofar as and as long as a certain group of the population remains 'unprotected' against the spread of this infection due to certain social conditions. With the change of these conditions, as well as with the implementation of appropriate preventive measures, the pandemic character of such infections more or less quickly disappears (results of the fight against malaria, trachoma, ankylostomiasis, tbc, etc.). With the establishment of rational measures to combat influenza, it can of course also be achieved such a state when it will be possible to counteract its spontaneous pandemic spread. Thus, the main cause of the transition of one or another infectious disease in terms of its growth and territorial spread into the state of P. are ultimately the social living conditions of the population, and the fight against them must proceed along the lines of broad economic and sanitary measures (see more detailed articles Epidemiology, Epidemics). L. Gromashevsky. PANDY REACTION (Pandy) was proposed by Pandy in 1910 for the qualitative determination of globulins in cerebrospinal fluid. The reagent is a solution of carbolic acid, according to the author: 1.0 Ac. carbol. crist. in 15 cm³ Aq. dest. The best reagent, however, is obtained according to the prescription of Zalozetsky (Zaloziecki)-10 cm³ Ac. carbol. liquefacti are well shaken in 100 cm³ Aq. dest. and placed in a thermostat (37°) for several hours, then left at room temperature until completely clarified. The settled transparent liquid is decanted from the layer of undissolved acid and used as a reagent. The reagent becomes cloudy from cold (it clears again when heated) and from standing in an open vessel. A persistently cloudy reagent is not suitable for the reaction. The reaction is performed (according to Grache) as follows: into a watch glass placed on a black background, the reagent is poured and 1 drop of cerebrospinal fluid is dripped into the reagent. At the point of contact of the liquid with the reagent, a cloudiness of varying degrees, from a light veil to a milky-white cloud, gradually spreading, is formed immediately. Mild degrees of reaction are well captured when illuminated from below (with an electric lamp). The Pandy reagent precipitates mainly the globulins of the cerebrospinal fluid. P. r. is more sensitive than Nonne-Apelt reaction of the first phase (see Nonne-Apelt reaction) and reveals the presence of globulins where the latter gives a negative result. According to Zalozetsky, a positive P. r. is obtained with a total protein content of 0.3 ‰/₀₀, which corresponds to the protein content in normal fluid (upper limit), therefore a mild degree of reaction is not yet a sign of pathological changes in the fluid. The diagnostic value of P. r. is the same as that of Nonne-Apelt reaction. The advantage over the latter is that for P. r. only a small amount of cerebrospinal fluid is required. The dissociation between both reactions described by some authors cannot yet be considered pathognomonic for any disease of the nervous system.