Circulation of influenza A and B in the Czech Republic from 2000-2001 to 2015-2016

BACKGROUND: To improve national influenza vaccination recommendations, additional data on influenza A and B virus circulation are needed. Here, we describe the circulation of influenza A and B in the Czech Republic during 16 seasons. METHODS: This was a retrospective analysis of data collected from the 2000–2001 to 2015–2016 influenza seasons by the Czech Republic national influenza surveillance network. Influenza was confirmed and viral isolates subtyped by virological assays followed by antigen detection or by reverse transcriptase-polymerase chain reaction. RESULTS: Of 16,940 samples collected, 5144 (30.4%) were influenza-positive. Influenza A represented 78.6% of positive cases overall and accounted for more than 55.0% of all influenza cases in every season, except for 2005–2006 (6.0%). Both A/H1N1 and A/H3N2 were detected in most seasons, except for 2001–2002 and 2003–2004 (only A/H3N2), and 2007–2008 and 2009–2010 (only A/H1N1). Influenza B represented 21.4% of positive cases overall (range, 0.0–94.0% per season). Both influenza B lineages were detected in three seasons, a single B lineage in 11, and no B strain in two. For the 11 seasons where influenza B accounted for ≥20% of positive cases, the dominant lineage was Yamagata in six and Victoria in four. In the remaining season, the two lineages co-circulated. For two seasons (2005–2006 and 2007–2008), the B lineage in the trivalent influenza vaccine did not match the dominant circulating B lineage. CONCLUSIONS: In the Czech Republic, during the 2000–2001 to 2015–2016 influenza seasons, influenza virus circulation varied considerably. Although influenza A accounted for the most cases in almost all seasons, influenza B made a substantial, sometimes dominant, contribution to influenza disease.