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Influenza surveillance in N. Greece during 1983-1993
V Kyriazopoulou1, F Frantzidou, S Alexiou
1National Influenza Centre for N. Greece, Medical School, Aristotelian University of Thessaloniki, Greece.
Abstract:
Following the WHO programme to monitor influenza, the National Influenza Centre for N. Greece presents the results of a laboratory surveillance during 1983-93. Influenza viruses were isolated every year except for 1986-87 and 1987-88 seasons. Type A viruses predominated in 1983-84, 1985-86, 1988-89 and 1989-90. Type B viruses were prevalent in 1990-91 and 1992-93. Both types of A and B viruses circulated concurrently in the community during the winters of 1984-85 and 1991-92. Seroconversions (CF tests) occurred each year against A, B or both types of influenza viruses. In 1986-87 and 1987-88 when no viruses were recovered, there were seroconversions to B viruses, suggesting influenza B activity in the area. Serological surveys by haemagglutination inhibition (HI) tests were also conducted in 1986-87 and 1988-89. The patterns of the isolated strains were similar to those recorded worldwide at the same time. There have been however differences in the virulence of the viruses and the duration of influenza seasons in this part of the world during 1983-93.
Insights
Influenza surveillance in N. Greece (1983-93) revealed yearly virus circulation, with Type A and B viruses showing distinct prevalence patterns. Despite some seasons lacking virus recovery, serological data confirmed ongoing influenza activity and highlighted regional variations in virulence and season duration.
Area of Science:
- Virology
- Epidemiology
- Public Health
Background:
- The National Influenza Centre for N. Greece participated in the World Health Organization's influenza monitoring program.
- Laboratory surveillance data from 1983 to 1993 were analyzed to understand influenza virus activity in the region.
Purpose of the Study:
- To present the results of a decade-long laboratory surveillance of influenza viruses in N. Greece.
- To characterize the temporal patterns of influenza A and B virus circulation and seroconversions.
Main Methods:
- Isolation and identification of influenza viruses from patient samples.
- Complement fixation (CF) tests to detect seroconversions against influenza A and B viruses.
- Haemagglutination inhibition (HI) tests for serological surveys in specific seasons.
Main Results:
- Influenza viruses were isolated annually, except during the 1986-87 and 1987-88 seasons.
- Type A viruses predominated in several seasons, while Type B viruses were prevalent in others; co-circulation occurred in two winters.
- Seroconversions were detected yearly, including to influenza B during seasons with no virus recovery, indicating B virus activity.
Conclusions:
- Influenza virus activity, including Type A and B, was consistently detected in N. Greece throughout the study period.
- Serological data provided crucial evidence of influenza activity, even when virus isolation was unsuccessful.
- The study identified variations in influenza virus virulence and season duration in N. Greece compared to global patterns.