[Immunological precursors of influenza epidemics].

The authors studied the immuno-epidemiological manifestations of ciculation and variability of the influenza virus during the periods preceding the officiallly recorded rise of the incidence of this disease. The following epidemic precursors were revealed: a) an increase of the number of persons who fell sick with subclinical form of the disease, accompanied by a rise in the population of the antibody level to the type of influenza virus whose latest variant later caused an epidemic morbidity elevation; b) a progressive predominance of the causative agent of the developing epidemic in the etiology of influenza; c) a growth of the collective immunity indices from the "minimal" to the "critical" levels; d) an increase of the sero-conversion multiplicity and of the antibody level in those who sustained the disease during the epidemic development. These precursors could be revealed at the period of from 1 1/2 to 6 months before the beginning of the morbidity growth caused by viruses of endogenous or of exogenous origin.