[Virological and serological examination of the patients in a period of influenza A1 outbreak in Aktyubinsk].

In October--December, 1977, an epidemic outbreak of influenza predominantly among young people of an organized community was recorded in Aktyubinsk. For decifering the outbreak virological and serological examinations of 325 subjects in foci of the disease as well as hospitalized patients were carried out. The etiology of influenza was confirmed clinically, epidemiologically, and by laboratory examinations in 150 patients. In chick embryos, 53 strains of influenza A1 virus were isolated. Investigations of the strains causing the influenza outbreak in autumn 1977 confirmed that they were influenza A (HINI) viruses. Antihemagglutinating antibodies to the new influenza A1 virus isolate were demonstrated in patients and normal subjects. A detailed analysis of antibody levels to 5 serotypes of influenza virus revealed a rise in antibody titers to the homologous serotypes A2 and to the new A1 isolate. In the acute stage of the disease and in convalescence the geometric mean antibody titer to the new A1 isolate was comparatively lower than to other serotypes.