Influenza and other acute respiratory infections take a high annual toll in terms of morbidity and mortality and can have a significant social impact. These respiratory infections can sometimes be avoided by vaccination. That is why an extensive surveillance system has been developed for this, both at national and European level.
Sciensano monitors the occurrence of both clinical respiratory infections and certain respiratory germs and reports the results weekly in the Acute Respiratory Infections Bulletin in French or in Dutch in order to provide information for healthcare providers, health authorities and the general population.
Sciensano was appointed by the Influenza Interministerial Committee in 2006 to carry out all human influenza surveillance activities in Belgium.
The surveillance of acute respiratory infections includes 4 units that work together and manage the surveillance by the sentinel networks:
- the Viral diseases service of Sciensano, which is recognised as the National Reference Center (NRC) Influenza and forms part of the Global Influenza Surveillance and Response System of the World Health Organisation
- the Epidemiology of infectious diseases Epidemiology service
- the Health services research service
- the Healthcare-associated and antimicrobial resistance service
The surveillance is based on the networks of sentinel general practitioners, sentinel laboratories, sentinel residential care centres and sentinel hospitals.. Within these networks, healthcare providers register clinical data and/or test results for patients who meet a specific case definition of an acute respiratory infection. In addition, a sample is taken from a selection of these patients via a nasal swab, which NRC influenza then tests for 16 respiratory viruses.
The networks are:
GP practices
The sentinel network of GP practices includes about 100 general practitioners, spread across the country. They report weekly on a number of health topics (including flu-like complaints and other acute respiratory infections).
Sentinel laboratories
The network of sentinel laboratories includes about 100 microbiology laboratories, spread across the country. They report the number of positive tests for about 40 germs on a weekly basis.
Sentinel hospitals (SARI network)
6 general hospitals have been participating in the Belgian SARI (Severe Acute Respiratory Infections) surveillance programme since 2012. The hospitals are located in the 3 regions of Belgium (2 hospitals in Flanders, 2 in Wallonia and 2 in Brussels). All hospital departments participate in the surveillance.
The purpose of the surveillance is to detect increased severity of seasonal flu and other acute respiratory infections in a timely manner and report this to the Belgian health authorities; to identify the circulating viruses and describe their characteristics and contribute to the estimation of the severity of epidemics or pandemics by the European institutions (ECDC/WHO-Euro).
On admission and discharge, the hospitals collect clinical data and a nasal swab is taken from every patient who meets the case definition for analysis by the NRC Influenza.
An admission for SARI is defined as
- a hospital admission of at least 24 hours,
- for severe symptoms of acute respiratory infection, defined as fever (≥ 38°) and (cough and/or shortness of breath)
- which occurred suddenly (in the last 10 days before admission),
- in which nosocomial infections are excluded.
Sentinel residential care centres
Sciensano recently set up a network of sentinel residential care centres. During the winter months, clinical data is collected from all residents with flu-like symptoms and during periods with high frequency of flu symptoms, a sample is also collected via a nasal swab.
The integrated results of these surveillance activities provide information on:
- the duration and intensity of the annual respiratory infection epidemics
- the respiratory viruses circulating
- the impact and severity of the epidemics
- resistance to antivirals
- effectiveness of the flu vaccine.
As winter mortality is partly attributable to acute respiratory infections, the data from these surveillance activities are used in the analysis of general excess mortality in the Be-MOMO surveillance of general excess mortality by the Epidemiology of infectious diseases service. The results of both surveillance activities are published jointly on a weekly basis in the Acute Respiratory Infections Bulletin.
Finally, the Quality of Vaccines and Blood Products service, as the Belgian Official Medicines Control Laboratory (OMCL), is responsible for the quality control of the influenza vaccines before they can be placed on the European market.