Surveillance of influenza in the post-pandemic period in Vojvodina, Serbia, October 2010-May 2015

Introduction/Objective In August 2010, World Health Organization declared the beginning of the post-pandemic phase of influenza surveillance. The aim of this study was to evaluate the epidemiological and virological characteristics of influenza and correlation between the influenza occurrence and weather conditions. Methods We used surveillance reports of influenza and laboratory data from October 2010 to May 2015. Data for the analysis were collected through sentinel surveillance of influenza-like illness (ILI), severe acute respiratory illness (SARI), acute respiratory distress syndrome, and by virological surveillance. The nasal and throat swabs from all influenza cases were performed by the PCR laboratory method. Results During the observed period, the highest rates of ILI were registered during the 2010/11 and 2012/13 seasons, with influenza A (H1N1) pdm09 and influenza B being predominant, respectively. The highest weekly age-specific rates of ILI were registered in school-age children (ages 5-14). Out of 1,466 samples collected, 720 (49.1%) were laboratory confirmed as influenza, and influenza A virus was more frequently detected than influenza B. Among confirmed cases of influenza, participation of patients with SARI or ILI was nearly equal (46% vs. 44.1%). There was a weak correlation observed between the decrease in temperature and rainfall and the increase in influenza detection (p = -0.04214 vs. p = -0.01545, respectively, p > 0.05). Conclusion There is a need for continuous surveillance in order to predict seasonal trends and prepare for a timely response to influenza outbreak.