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Influenza in Poland in 2011-2012 and in 2011/2012 and 2012/2013 epidemic seasons.

UNLABELLED
This paper aimed at evaluating the epidemiological situation of influenza in Poland in 2011-2012 and in 2011/2012 and 2012/2013 epidemic seasons and comparing it with the situation observed in the previous years.


MATERIAL AND METHODS
An analysis was mainly based on three sources of data: (1) bulletins "Infectious diseases and poisonings in Poland in 2012" and "Vaccinations in Poland in 2012" (NIPH-NIH, CSI. Warsaw 2013) and analogically former bulletins, (2) "Reports on influenza cases and persons suspected of influenza", sent in 2013 and previous years to the Department of Epidemiology, NIPH-NIH by the Voivodeship Sanitary- Epidemiological Stations, (3) data of the Department of Influenza Research, National Influenza Centre, NIPH- NIH - results of virological testing performed in 2011/2012 and 2012/2013 epidemic seasons in the National Influenza Centre and/or laboratories of the Voivodeship Sanitary-Epidemiological Stations (VSES) within influenza surveillance - Sentinel as well as beyond this system. Data on influenza cases come from aggregated notifications which are sent obligatorily to the VSES by all health care units and physician practices. Influenza, influenza-like illness and acute respiratory infections, i.e. cases meeting the criteria recommended in influenza surveillance in the European Union are subject to mandatory notification.


RESULTS
In 2011-2012, there was an increase in the number of influenza and influenza-like illness cases in Poland compared to 2010, i.e. 2- and 2,5-fold, respectively. In 2011, a total of 1 156 357 cases were reported and incidence amounted to 3 001.5 per 100,000 population (11 014.5 in age group 0-4 years). As many as 0.51% of infected persons were referred to hospital. According to the CSO data, 95 fatal cases of influenza were notified. Influenza vaccination coverage was 2.8%. In 2012, 1 460 037 cases were registered and incidence was 3 789.0 (17 807,1 in age group 0-4 years). A total of 0.33% of influenza cases were referred to hospital. As many as 4 deaths due to influenza were reported. Percentage of population vaccinated against influenza amounted to 2.3%. In 2011/12 epidemic season, 1 085 471 cases were noted and incidence was 2 816.6 per 100,000 population (12 792.3 in age group 0-4 years) while in 2012/13 epidemic season its number was nearly 3-fold higher, i.e. 3 025 258 cases and incidence - 7 851.0 (30 591.7 in age group 0-4 years). In both epidemic seasons, type A influenza subtype H1N1 and human respiratory syncytial virus (RSV) predominated in infections with influenza virus and other viral respiratory infections, respectively. Antigenic analysis of influenza strains showed their affinity with vaccine strains of the vaccines recommended for these epidemic seasons.


SUMMARY
An increase in the number of notified cases of influenza and influenza-like illness, which is recently observed in Poland, is significantly affected by the improving quality (especially sensitivity) of surveillance system, commenced in the 2009 influenza pandemic. This surveillance system, however, is still not sufficiently uniform and stable. Low percentage of population vaccinated against influenza suggests the ineffectiveness of influenza vaccine promotion campaigns conducted so far. An increase in the influenza vaccination coverage to the average observed in the EU countries should be one of the priorities for the sanitary-epidemiological stations.