Infections with Influenza A/H3N2/ Subtype in Poland in the 2016/2017 Epidemic Season

The 2016/2017 epidemic season was characterized by a lower number of diagnostically tested samples of the nasal and throat swabs and bronchoalveolar lavage fluid, compared with the preceding season. The predominant influenza subtype found was A/H3N2/ which was notably diagnosed in patients over 25 years of age. This subtype was also often diagnosed in older people of 65+ years, which is in line with the risk assessment prepared by the European Center for Disease Prevention and Control (ECDC) at the beginning of the season. The A/H3N2/ subtype was most often diagnosed in the West Pomeranian and Warmian-Masurian Voivodeships. In this epidemic season, there were 11 coinfections of the A/H3N2/ subtype with other influenza and influenza-like viruses recorded in Poland. A different situation had occurred in the 2014/2015 season, when the subtype A/H3N2/ also was predominant, but the virus was most commonly diagnosed in children up to 14 years of age. In both seasons, the least confirmations were observed in patients between 15 and 24 years.