[The epidemiological characteristics of Sonne and Flexner dysentery in St. Petersburg in 1953-1994].

In connection with the growth of mortality in Flexner's dysentery observed since 1991 and a rise in morbidity in this infection since 1993 the data on the registered cases of Shigella flexneri and Shigella sonnei infections in St. Petersburg for the period of 1953-1994 were analyzed. In the 60-80s the specific features of the epidemic process was determined by S. sonnei infection which constituted up to 90% of all documented cases of dysentery. Flexner's dysentery lost the character of a mass epidemic disease in the 60s, but in the 70s became again capable of epidemic spread, which was testified by annual seasonal rises producing a half of all cases registered per annum and two rises with peaks in 1975 and 1984. In 1991-1992 the tenfold rise of morbidity in Flexner's dysentery took place in the presence of a common level of morbidity of Shigella infections. In 1993-1994 an essential change in the etiological structures of Shigella infections was observed: morbidity in Flexner's dysentery rose 6 times and morbidity in Sonne dysentery dropped 3 times, which was probably due to socio-economical changes in the living conditions of the population during recent years.