Influenza in Poland in 2003

Following two years of low influenza incidence in Poland, the activity of this disease markedly increased in 2003. In total 1,216,285 cases of influenza like illness were registered (incidence 3,184.4 per 100,000). Regionally the incidence ranged from 1,195.7 in Zachodniopomorskie to 5,719.7 per 100,000 in Mazowieckie. Children and adolescents under 15 years of age accounted for 41.7% of all cases (507,102 cases, age specific incidence 7,579.0 per 100,000). In this age group the incidence varied regionally from 2,718.1 in Podlaskie to 14,087.6 per 100,000 in Mazowieckie. 3,128 patients (0.26% of all cases) required hospital admission. There were 141 deaths due to influenza (mortality 0.12%) in 2003, in 78.7% these were persons over 70 years of age. Nineteen strains of influenza virus were isolated in 2003 in Poland, including 15 strains of subtype A(H3), 3 strains of subtype A(H1) and one strain of type B. Besides, in other 10 cases influenza A infection was confirmed by direct immunofluorescence test. All isolated influenza strains were antigenically similar to the vaccine strains recommended for the epidemic season 2002/03 and 2003/04.