[Immune structure of the population of Moscow to the strains of the influenza viruses A(H3N2), A(H1N1) and B circulating in 1977].

Examinations for the presence of antihemagglutinins to influenza A(H3N2), A(H1N1) and B virus strains in the sera from people of different ages collected in April-May and October-November, 1977, showed that influenza A(H1N1) virus began to circulate in the human population of Moscow before the onset of an overt epidemic, in the period between June and October, 1977. This conclusion has been drawn on the basis of the absence of antihemagglutinins to A(H1N1) virus in the sera from subjects of 16-20 years late in April and their detection in 25.9% of those examined on November 23, 1977. The lack of antibody both to the old A/FM/1/47 (H1N1) and a new A/USSR/90/77 (H1N1) strains of influenza A (H1N1) virus in this age group in April indirectly attests to the fact that influenza A virus of this subtype has not circulated among the population in the last 20 years. At the same time the observed significant (by 1.5-2.0 log2) rise in the geometric mean titers of antibody to A(H3N2) virus in May-October indicates its continued active circulation among the population in this period. Thermostable inhibitors of influenza A/USSR/90/77 (H1N1) virus in human sera may be most effectively removed by treatment of the sera with potassium periodate or RDE.