Clinical surveillance of the influenza A(H1N1)2009 pandemic through the network of sentinel general practitioners

Since the 1950s, sentinel surveillance networks with general practitioners (GPs) have been progressively implemented and involved in influenza surveillance, e.g. in the UK, the Netherlands, Belgium, France, Portugal and Spain. Since 1988, several collaborative European studies with sentinel networks aimed at stimulating influenza surveillance all over Europe and harmonising the surveillance activities (1-3). In Belgium, a sentinel network specifically dedicated to influenza surveillance, with the participation of about 40 GPs, was initiated in 1985 (4;5) and has participated in various European influenza related projects. Since autumn 2007, this network is integrated into the network of the Sentinel General Practitioners (SGPs) existing since 1979 and responsible for the surveillance of many other health problems (6-8). Since then, the SGPs have been continuously involved in the clinical and virological influenza surveillance (9). As the SGPs network is not appropriate for the detection of sporadic cases, during the containment phase of the A(H1N1)2009 (from week 14 till week 28), a comprehensive surveillance of all suspected cases of A(H1N1)2009 virus among travellers returning from the USA, Mexico or other countries at risk, was carried out by all Belgian physicians. As of week 29, the start of the mitigation phase, the SGPs were the most important tool for the clinical as well as the virological influenza surveillance. The latter was reinforced with the purpose of following up the A(H1N1)2009 virus circulation in the general population (10).