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Type A influenza (H2N2) viruses isolated in Leningrad in 1980
Insights
Influenza A H2N2 virus caused outbreaks in Leningrad in 1980. Laboratory analysis confirmed these strains were similar but not identical to the A/Singapore/I/57 reference strain.
Area of Science:
- Virology
- Epidemiology
Background:
- Two independent outbreaks of influenza-like illness occurred in Leningrad in April-May 1980.
- Affected populations included children in a children's home and boarding-school pupils.
Purpose of the Study:
- To identify the etiological agent responsible for the influenza-like illness outbreaks.
- To characterize the isolated influenza A virus strains.
Main Methods:
- Isolation and characterization of influenza virus strains from affected individuals.
- Serological testing, including hemagglutinin inhibition tests and seroconversion analysis.
- Molecular-biochemical techniques for detailed strain analysis.
Main Results:
- Seven influenza A virus strains were isolated from children and one adult.
- All isolated strains were identified as influenza A H2N2 subtype.
- Significant seroconversion to H2 hemagglutinin was observed in affected individuals.
- The A/Leningrad/80 isolates were found to be similar but not identical to the A/Singapore/I/57 reference strain in polypeptide and gene composition.
Conclusions:
- The A/Leningrad/80 isolates represent the H2N2 sero-subtype of influenza A virus.
- These findings indicate the circulation of H2N2 influenza A virus in Leningrad during the study period.
- The isolated viruses exhibit genetic and antigenic similarities, yet distinct differences, compared to a historical reference strain.
Abstract:
In April-May 1980, two independent outbreaks of influenza-like illness occurred in Leningrad among children's-home children aged from 3 months to 2 years (of 68 children under observation, 50 became ill) and among boarding-school pupils aged 15-17 years (of 50 pupils under observation, 13 became ill). A total of five influenza A virus strains were derived from one clinically healthy and three affected children of the children's home. Similar viruses were obtained from one affected boarding-school pupil and from an infected woman aged 24 years (a sporadic case within a household). On the basis of laboratory findings, all these seven strains were identified as influenza A H2N2 subtype strains. Six of the affected children showed significant seroconversion only to H2 haemagglutinin from February to May 1980. Type A influenza H2N2 virus was isolated from three persons, including the sporadic case, who also showed significant seroconversion to H2 haemagglutinin. H2N2 influenza A virus was isolated on two occasions, at a 7-day interval, from the girl N. Ju. Laboratory findings obtained from the study of the viruses isolated using up-to-date immunological and molecular-biochemical techniques enable us to conclude the following. The A/Leningrad/80 isolates belong to H2N2 sero-subtype. The viruses isolated are similar but not identical to the A/Singapore/I/57 reference strain in details of polypeptide and gene composition.