Regional Diversification of Influenza Activity in Poland During the 2015/16 Epidemic Season

Epidemic Influenza Seasons from 2008 to 2018 in Poland: A Focused Review of Virological Characteristics

The objective of this review was to elaborate on changes in the virological characteristics of influenza seasons in Poland in the past decade. The elaboration was based on the international influenza surveillance system consisting of Sentinel and non-Sentinel programs, recently adopted by Poland, in which professionals engaged in health care had reported tens of thousands of cases of acute upper airway infections. The reporting was followed by the provision of biological specimens collected from patients with suspected influenza and influenza-like infection, in which the causative contagion was then verified with molecular methods. The peak incidence of influenza infections has regularly been in January-March each epidemic season. The number of tested specimens ranged from 2066 to 8367 per season from 2008/2009 to 2017/2018. Type A virus predominated in nine out of the ten seasons and type B virus of the Yamagata lineage in the 2017/2018 season. Concerning the influenza-like infection, respiratory syncytial virus predominated in all the seasons. There was a sharp increase in the proportion of laboratory confirmations of influenza infection from season to season in relation to the number of specimens examined, from 3.2% to 42.4% over the decade. The number of confirmations, enabling a prompt commencement of antiviral treatment, related to the number of specimens collected from patients and on the virological situation in a given season. Yet influenza remains a health scourge, with a dismally low yearly vaccination rate, which recently reaches just about 3.5% of the general population in Poland.

Respiratory Viruses in Different Provinces of Poland During the Epidemic Season 2016/2017

In Poland, influenza surveillance is conducted by 16 Provincial Sanitary Epidemiological Stations, headed by the Department of Influenza Research, National Influenza Center at the National Institute of Health - National Institute of Hygiene (NIPH-NIH). During the epidemic season 2016/2017, more than 4000 samples were tested for respiratory infections, with approximately 1800 positive results, the most of which were among patients over 65 years old. Most samples were tested in the Western Pomeranian province, but the greatest proportion of positively diagnosed influenza infections, amounting to 72.7% was noted in the Lodz metropolitan area in central Poland. Twenty five deaths due to post-influenza infections and complications were recorded across the country, of which 20 were among individuals over 65 years of age. During the 2016/2017 season, the dominant subtype was A/H3N2/, unlike the subtype A/H1N1/California/7/2009 during the previous season. A high number of confirmed infections of subtype A/H3N2/can attest to low vaccination rates.

Circulation of Influenza Virus in the 2015/2016 Epidemic Season in Poland: Serological Evaluation of Anti-hemagglutinin Antibodies

The diagnostic of influenza virus infections is possible using molecular biology methods as well as the analysis of anti-hemagglutinin (anti-HA) antibodies in the blood serum. The aim of this study was to determine the level of anti-HA antibodies in 7 age groups of patients during the 2015/2016 epidemic season in Poland. A total of 1050 serum samples were tested using the hemagglutination inhibition (HAI) assay. We confirmed the presence of anti-HA antibodies for the influenza virus strains: A/California/7/2009(H1N1)pdm09, A/Switzerland/9715293/2013(H3N2), and B/Phuket/3073/2013, which were the components of the influenza vaccine for the 2015/2016 epidemic season. The level of specific anti-HA antibodies was different in each age group. The geometric mean titers were highest at age 5-9 years, where the antibody protection level reached 61.3% against B/Phuket/3073/2013 and 52.7% for A/Switzerland/9715293/2013(H3N2) antigen. The antibody level amounted to 56.7% against for antigen B at age 45-64. In the remaining age groups, the protection levels for all hemagglutinin types did not exceed 50%. These findings confirm the urgent need to increase a persistently low influenza vaccination coverage in the Polish population, which may have had its part in the noticeable increase in the confirmed cases of influenza and influenza-like virus infection during the season.