INFLUENZA SURVEILLANCE IN NORTH GREECE DURING 1983-1993

Following the WHO programme to monitor influenza, the National Influen za Centre for N. Greece presents the results of a laboratory surveilla nce during 1983-93. Influenza viruses were isolated every year except for 1986-87 and 1987-88 seasons. Type A viruses predominated in 1983-8 4, 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. Seroconve rsions (CF tests) occurred each year against A, B or both types of inf luenza viruses. In 1986-87 and 1987-88 when no viruses were recovered, there were seroconversions to B viruses, suggesting influenza B activ ity 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 s ame time. There have been however differences in the virulence of the viruses and the duration of influenza seasons in this part of the worl d during 1983-93.