Objectives:

Acute respiratory infections (ARI) are very common in the general population: In the Netherlands, yearly 3.2 million patients visit general practitioners with symptoms of upper respiratory disease. To reduce diagnostic deficit, we studied the incidence and aetiology of ARI. Additionally, we studied ARI risk factors, healthcare demand and burden of disease.

Methods:

From October 2000 to October 2003, the incidence of influenza-like illness (ILI) and other ARI in general practices and the role of a broad range of pathogens in the Netherlands were studied. General practitioners from a Dutch sentinel network registered all patients consulting them for ILI and other ARI. Weekly, general practitioners randomly sampled one of these patients (case) and one patient of the same age group, visiting the general practitioner for non-respiratory symptoms (control). Samples were analysed for respiratory viruses and bacteria. Participating patients completed a questionnaire on risk factors and burden of disease.

Results:

Forty practices registered all patients consulting them for ILI or other ARI. Twenty practices participated in the case-control study. Per year on average, 1600 consultations for ILI and 5000 for ARI were registered, leading to an incidence of 130 and 410 per 10 000 persons respectively. In total 647 cases and 559 controls were sampled. In more than 65% of the ILI cases and 50% of the ARI cases, viruses were detected, compared with 20% in controls. Bacteria were detected in more than 30% of both cases and controls.

Conclusion:

Despite three unusual calm influenza seasons, influenza was the most common pathogen in ILI-patients. Rhinovirus was most often detected in ARI patients. Incidence for both ILI and ARI was highest for 0–4-year olds. More data on the incidence of ILI and ARI and associated pathogens will be presented.