Surveillance of respiratory pathogens and influenza-like illnesses in general practices - The Netherlands, winter 1997/98.

The Netherlands Institute of Primary Health Care (NIVEL) has coordinated the activities of a sentinel surveillance network of 43 general practices since 1970. These practices care for 1% of the Dutch population, a sample representative of the national population in terms of age, sex, and degree of urbanisation (1). NIVEL uses data from the network to calculate the incidence of influenza-like illness each week during the winter season. At the request of NIVEL, the system has been enhanced since the winter of 1992-93 by the National Institute of Public Health and the Environment (Rijksinstituut voor Volksgezondheid en Milieu - RIVM, to include virus isolation and detection from nose/throat swabs obtained from patients with acute upper respiratory tract infections (ARI), of which on average influenza-like illness accounts for about 62%. This article presents the main findings of the surveillance of influenza-like illness and other ARI in general practice in the Netherlands in the winter of 1997/98, assesses the relationship between influenza virus isolation and influenza-like illness registration, and compares virus isolation and polymerase chain reaction (PCR) analysis for respiratory syncytial virus (RSV), rhinovirus, and enterovirus