2014/2015 Influenza season in an inland portuguese region

Influenza surveillance is an important tool to identify emerging/reemerging strains, and defining seasonality of the circulating strains. The aim of this work is to compare the circulating strains detected by Centro Hospitalar da Cova da Beira, EPE,(CHCB) from an inland north region of Portugal, with the strains circulating among Europe during2014/2015 Influenza season. In the present review, 249 nasofaringeal swabs received in were analized by real time PCR techniques, designed to amplify Influenza A and Influenza B virus. All the positive samples were sent to the Portuguese reference Laboratory in order to subtype influenza A virus and to perform genetic and antigenic characterization of the detected viruses. During 2014/2015 season, a total of 109 positive cases (62 Influenza A and 47 Influenza B) - were detected in the studied region. In the present season, all seasonal types/subtypes of influenza virus circulated, inspite of low level circulation of the Influenza A(H1)pdm strain (~5%of the positive samples, circulating between 6/2015-9/2015 weeks). A(H3) and B strains co-circulated between weeks 1/2015 and 11/2015 with peak activity in weeks 6 and 7/2015. Influenza A, excluding A(H1)pdm, was responsible for 47% of positive cases, mainly in the last 6 weeks. Influenza B strains were responsible for 42% of positive Influenza cases, mainly in the first 7 weeks of the year. All influenza B strains characterized by the Portuguese National Laboratory were from B/Yamagata lineage. 19% of influenza B strains wereselected for genetic characterization, all were similar to B/Phuket/3073/2013 (clade 3). At the date of submission of the abstract, only 8 Influenza A strains were genetically characterized, 5 belonged to genetic subgroup 3C.2a, represented by A/Hong Kong/5738/2014, dissimilar to the current A(H3N2) vaccine strain and 3 belonged to A/Samara/73/2013 (genetic group 3C.3), antigenically similar to the current A(H3N2) vaccine The co-circulation of influenza types/subtypes was similar to the one described in Europe, but in this Portuguese region, the Influenza B circulated in first part of the epidemic period, followed by A(H3) virus at the end of epidemic period.. The genetic characterization observed in Portugal was similar to the one from ECDC data for Influenza B. Relatively to Influenza A, the majority of detected viruses were dissimilar to the 2014/2015 A(H3) vaccine virus, being a higher proportion than the observed in Europe, but more data is needed to achieve any conclusion.