Characterization and circulation of seasonal influenza viruses in Madrid, 2010‐2016

Abstract

Influenza virus infection is a major health care burden and is associated with significant morbidity and mortality. The 2009 influenza pandemic highlighted the importance of influenza surveillance. The objective of this study was to assess the epidemiology and activity of influenza A and B viruses in adults and children in the post-pandemic period with a special focus on the pediatric population. We performed a retrospective descriptive study involving adults and children with influenza-like illness at the Clinico San Carlos Hospital (Madrid, Spain) over six influenza seasons, between August 2010 and April 2016. Respiratory specimens were collected from 3131 patients and routinely processed for influenza diagnosis. Epidemiological analysis was performed in terms of gender, age, and seasonal distribution. Globally, Influenza A and B viruses were detected in the respiratory specimens of 696 (22.2%) of the 3131 studied population. Among all influenza positive specimens, 142 (20.4%) were influenza A(H1N1)pdm09, 61 (8.8%) were influenza A(H3N2), 321 (46.1%) were untypeable influenza A viruses and 166 (23.9%) were influenza B. Co-infection by both influenza A and B viruses was detected in six patients (0.9%). Meanwhile, co-infection with other non-influenza respiratory viruses was identified in 5 children and 20 adults. Influenza A(H1N1)pdm09 virus activity has been significantly high since the 2009 pandemic and has gradually replaced the previously circulating seasonal influenza A(H1N1) virus. Moreover, influenza A(H3N2) virus activity remained at low levels during the last winter season while influenza B virus isolates increased significantly over the past 2 years.

Heterogeneous estimates of influenza virus types A and B in the elderly: Results of a meta‐regression analysis

“…Following duplicate removal (N = 946) and the screening of titles and abstracts (N = 5787), a total of 43 records were deemed to be worthy of further evaluation and the corresponding full texts were assessed. Of these, 16 papers met all inclusion criteria and were included. In the study by Caini et al only 12 of 26 study locations had a sufficient number (≥100) of isolates among the elderly.…”

“…A comprehensive literature search was conducted; this included both automatic and manual modalities. As the authors of this study were aware that several studies on the outcomes of interest were available, the automatic search strategy was constructed in several steps until all known studies appeared among the search results. To do this, it was first assumed that studies reporting the frequency of IVB would also report that of IVA.…”

Clinical and demographic characteristics of influenza b outbreak in Erzincan province of Turkey

“…Recent studies report significant increases in IB infections. The incidence of IB has been reported as 23.9% in a study from Spain, conducted between 2010 and 2016 [17]. There are several studies demonstrating that IB is more dominant in some periods in the epidemiology of seasonal influenza.…”

Epidemiology and Clinical Features of Seasonal Influenza Cases Followed in Our Clinic

“…Influenza, commonly known as the "flu", is a highly contagious viral infection and one of the most severe diseases, representing a major cause of acute upper respiratory tract infections worldwide [1] . These viruses can cause seasonal epidemics, manifesting as an acute febrile disease with variable degrees of severity, ranging from mild fatigue to respiratory failure and death [1] . Due to the epidemics caused by the virus, an average of 3-5 millions of diseases and 250-500 thousands of deaths are seen annually in the world [2] .…”