Severe Acute Respiratory Infections (SARI) in Belgium (2011-2020)

The Belgian Severe Acute Respiratory Infections network (BELSARI-net) was implemented during the influenza season 2011-2012 following the recommendations of the World Health Organization (WHO) to monitor severity of influenza viruses in hospitals. The network is composed of 6 hospitals throughout the country, two in each administrative region (Flanders, Wallonia and Brussels-Capital), and operates during the influenza epidemic period (from the last week of December or first/second week of January to the third/last week of April, depending on when influenza virus circulation is detected by the general population, based on the Influenza-like illness (ILI) network of general practitioners). Enrollment is performed for all cases matching the SARI case definition (based on WHO's case definition) and accepting to take part. A respiratory specimen is sampled systematically from each participant, and detailed clinico-epidemiological data, such as information on age, sex, symptoms and potential risk factors such as pregnancy or comorbidities (chronic respiratory diseases, asthma, chronic cardiovascular diseases, renal insufficiency, obesity, diabetes, hepatic or renal insufficiency, immunodeficiency, neuromuscular disease, pregnancy) is also collected. Participants are followed up during hospitalization for the occurrence of complications (detection of pneumonia based on chest radiography, development of acute respiratory distress syndrome (ARDS), requirement for respiratory assistance and/or for extracorporeal membrane oxygenation (ECMO), admission in intensive care unit (ICU)), or death (all-cause death). The current project includes all the samples received by the Belgian National Influenza Centre (NIC) during the influenza seasons 2011-2012 till 2019-2020.