Diagnosing the two main epidemic respiratory viroses: influenza and respiratory syncytial virus infections. Role of molecular virology.

The virologic diagnosis of respiratory syncytial virus (RSV) or influenza virus infections is useful in cases of severe respiratory diseases in hospitalized children and adults, and in the French influenza survey network. The conventional tools used for virologic diagnosis include direct antigen detection by immunofluorescence (IFA) or an immunoenzymatic test (ElA), and viral isolation technique (VIT). In most cases, IFA and EIA have a slightly lower sensitivity than WT but, on the other hand, are able to detect at least as many IFA- or EIA-positive and WT-negative samples. The results of several teams, using various PCR technologies to search for influenza virus or RSV sequences in respiratory samples, show that the molecular methods detect more positive cases than the conventional fools. During the influenza epidemic, the detection rate of influenza A virus varies from 57 to 64%, and from 38 to 50% for PCR and VIT; respectively. The PCR assays are able to detect from 57 to 62% of RSV-positive samples, whereas WT and/or IF have an average of only 43% for RSV-positive samples. These results underline the limits of traditional methods. (C) 2000 Editions scientifiques et medicales Elsevier SAS.