Prevalence and seasonality of viral respiratory infections in a temperate climate region: A 24-year study (1997-2020).

BACKGROUND: Few long-term reports have been published on the epidemiology of respiratory viruses despite their frequent involvement in extremely common infections. The aim here was to determine the frequency and distribution of respiratory viruses in a temperate climate area (Barcelona, Spain) throughout a 24-year period. METHODS: We collected data on all respiratory viruses detected from 1997 to 2020 in our institution. Clinical specimens were analyzed mainly by conventional techniques, and molecular techniques were also used. RESULTS: Of the 59,579 specimens analyzed, 21,382 (35.9%) were positive for at least one virus. The number of positive samples during cold months was significantly higher than in warm months. Respiratory virus infections were detected in patients of all ages, above all in children under 3 years of age, who were most frequently infected with the respiratory syncytial virus, whereas Influenza A virus predominated in the other groups, especially in adults. A clear demographic and seasonal pattern was established for some viruses. Circulation of other respiratory viruses during the FLUAV H1N1pdm09 and SARS-CoV-2 pandemics was observed. CONCLUSIONS: This long-term study provides new knowledge about the prevalence of respiratory viruses in a Mediterranean region. Throughout the study period, the frequency of some viruses remained constant, whereas others varied with the year. A clear demographic and seasonal pattern was established for some viruses. Patients suffering from severe respiratory infections should be examined for a range of respiratory viruses regardless of gender, age, or season.

Benefits and drawbacks of molecular techniques for diagnosis of viral respiratory infections. Experience with two multiplex PCR assays.

Molecular techniques have represented a major step forward in the diagnosis of viral respiratory infections. They are considered highly sensitive and specific compared to conventional techniques. In this study two nucleic acid amplification tests (NAATs) were compared to conventional methods (immunofluorescence and viral culture). The aim of this work was to discuss the clinical interpretation of the results obtained by NAATs on the basis of the two-decade experience of our group and the literature. Eighty nasopharyngeal aspirates were collected from children under six years attended for acute respiratory illness at the pediatric emergency room of a third level Hospital. Both NAATs tested (Seeplex(®) and Clart(®)) showed an overall higher performance regarding sensitivity (76% and 90%, respectively). Compared to Seeplex(®), the Clart(®) system tripled the number of multiple detections (8 by Seeplex(®) vs. 25 by Clart(®)). In some specimens both NAATs detected different viruses. Given these discrepancies and the fact that detection of viral nucleic acids is not necessarily related to the current clinical syndrome, the interpretation of molecular results may not always be so straightforward. The pros and cons of NAATs should always be taken into account when giving a result.