Virologische NIVEL/RIVM-surveillance van respiratoire virusinfecties in het seizoen 1994/95

Abstract

The Netherlands institute of primary health care (NIVEL) is running a surveillance network of 46 sentinel general practices (GP) stations, spread over the country in proportion to the population density. The GP of this network sent nose/throat swabs from the part of their patients with respiratory illnesses to the RIVM. In the season 1994/95 557 respiratory specimens were examined by virus isolation and PCR. In 189 (34%) of the samples a respiratory virus or bacterium was detected by either technique. Influenza B (9%) and rhinovirus (9%) were the predominant viruses followed by coronavirus OC43 (4%), influenza A virus (3%), RS virus (3%), and adenovirus (2%). In 8 (4%) of the positive samples two etiologic agents were detected. In 70 (37%) of the causative agents were only recognized by PCR. When comparing the results of the surveillance among patients in the GP network with those of the examinations of virus diagnostic laboratories, the main differences were the higher proportion of influenza virus isolations and the lower proportion of RS virus isolations in the GP system. Among the isolated influenza viruses, type B prevailed in the GP system and type A(H3N2) in the virus diagnostic laboratories. From 68 PCR-positive patients 72 follow-up samples could be obtained, taken on an average 24 days after the first specimen. In only three patients the agent could still be demonstrated in the follow-up sample ; in two of these the agent was Chlamydia pneumoniae. Conclusions: The proportions of at least part of the viruses isolated from patients with respiratory complaints in a GP network differ considerably from those isolated in virus diagnostic laboratories, the samples of which are mainly derived from hospitalised patients. Surveillance of respiratory infections among patients of GP is therefore essential for the insight in the epidemiology of respiratory diseases. On the average, illness from infection with influenza B-virus appears to be less severe compared to influenza A(H3N2) virus. Application of the PCR-technique enhances considerably the rate of positive results of the examination of respiratory specimens. Important respiratory pathogens as coronavirus, Mycoplasma pneumoniae, and Chlamydia pneumoniae even can only be detected by PCR. The clinical relevance of the PCR-technique appears to be high for the tested respiratory viruses and for Mycoplasma pneumoniae. The rhinovirus PCR and the virus culture technique should be improved, whereas the bacterial surveillance should be extended to important cultivable respiratory bacteria.