Molecular diagnosis of communal respiratory viral infections

The diagnosis of respiratory viral infections in the community caused by influenza virus, parainfluenza virus (PIV), respiratory syncytial virus (RSV), adenovirus, rhinovirus and coronavirus is based on viral isolation techniques and on direct antigen detection by immunofluorescence assay (IFA) or an immunoenzymatic test (EIA). It has been shown that, in most cases, the molecular methods, i.e. the polymerase chain reaction (PCR) assays, are able to detect more positive cases than the conventional tools. According to the results of three distinctive groups, the detection rate of influenza A viruses, evaluated inside an epidemic period, reaches 57,5, 57,1, 57,7 % and 38,9, 50, 40,9 %, for PCR assays and VIT, respectively. In three distinctive studies of RSV infections, the PCR assays are able to detect 61,3, 62, 62,4 % of VRS-positive samples, whereas there are 65,3, 44, 39,3 % of VIT and/or IF positive samples. For the other respiratory viruses : PIV, AdV, RV, CV few data are available on the PCR results. We have previously shown in epidemiological studies in children, that PCR assays may increase the detection rates of PIV from 4,3 to 8,3 %, of AdV from 9,6 to 15,2 %, and of RV from 15,6 to 39,7 % during a RV outbreak in spring. But if the high sensitivity of the PCR assays and its possible standardization and automatisation, points out the limits of the conventional methods, it remains clear that their use as a diagnostic tool is related to the clinical meaning that will be given to the detection of a viral sequence in a respiratory sample.