BackgroundWell-established influenza surveillance systems (ISS) can be used for respiratory syncytial virus (RSV) surveillance. In Portugal, RSV cases are detected through the ISS using the European Union (EU) influenza-like illness (ILI) case definition.AimTo investigate clinical predictors for RSV infection and how three case definitions (EU ILI, a modified EU acute respiratory infection, and one respiratory symptom) performed in detecting RSV infections in Portugal.MethodsThis observational retrospective study used epidemiological and laboratory surveillance data (October 2010–May 2018). Associations between clinical characteristics and RSV detection were analysed using logistic regression. Accuracy of case definitions was assessed through sensitivity, specificity, and area under the receiver operating characteristic curve (AUC). A 0.05 significance level was accepted.ResultsThe study involved 6,523 persons, including 190 (2.9%) RSV cases. Among 183 cases with age information, RSV infection was significantly more frequent among individuals < 5 years (n = 23; 12.6%) and ≥ 65 years (n = 45; 24.6%) compared with other age groups (p < 0.0001). Cough (odds ratio (OR): 2.4; 95% confidence interval (CI): 1.2–6.5) was the best RSV-infection predictor considering all age groups, while shortness of breath was particularly associated with RSV-positivity among ≤ 14 year olds (OR: 6.7; 95% CI: 2.6–17.4 for 0–4 year olds and OR: 6.7; 95% CI: 1.5–28.8 for 5–14 year olds). Systemic symptoms were significantly associated with RSV-negative and influenza-positive cases. None of the case definitions were suitable to detect RSV infections (AUC = 0.51).ConclusionTo avoid underestimating the RSV disease burden, RSV surveillance within the Portuguese sentinel ISS would require a more sensitive case definition than ILI and, even a different case definition according to age.

A B S T R A C TIntroduction: Respiratory syncytial virus (RSV) is associated with substantial morbidity and mortality since it is a predominant viral agent causing respiratory tract infections in infants, young children and the elderly. Considering the availability of the RSV vaccines in the coming years, molecular understanding in RSV is necessary. Objective: The objective of the present study was to describe RSV epidemiology and genotype variability in Portugal during the 2014/15-2017/18 period. Material and methods: Epidemiological data and RSV-positive samples from patients with a respiratory infection were collected through the non-sentinel and sentinel influenza surveillance system (ISS). RSV detection, subtyping in A and B, and sequencing of the second hypervariable region (HVR2) of G gene were performed by molecular methods. Phylogenetic trees were generated using the Neighbor-Joining method and p-distance model on MEGA 7.0. Results: RSV prevalence varied between the sentinel (2.5%, 97/3891) and the non-sentinel ISS (20.7%, 3138/ 16779), being higher (P < 0.0001) among children aged < 5 years. Bronchiolitis (62.9%, 183/291) and influenza-like illness (24.6%, 14/57) were associated (P < 0.0001) with RSV laboratory confirmation among children aged < 6 months and adults ≥65 years, respectively. The HVR2 was sequenced for 562 samples. RSV-A (46.4%, 261/562) and RSV-B (53.6%, 301/562) strains clustered mainly to ON1 (89.2%, 233/261) and BA9

Analysis of 16S rRNA gene alone is insufficient for the accurate identification of NTM. A stepwise algorithm combining 16S rRNA and hsp65 gene analysis by multiple public databases is proposed to identify NTM at the species' level.

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ResultsOver the study period were detected 114 (5.2%) RSV in 2187 tested NPS. Of these 67 (59%) were from subtype A and 47 (41%) from subtype B. ConclusionsOur study highlights the importance of RSV in ILI cases, showing a seasonal circulation each winter season during influenza epidemic. RSV accounted for 5.2% of the cases reported in the scope of influenza surveillance, assuming a huge importance in young children and elderly. Molecular data for RSV A revealed co circulation of NA1 and ON1 between 2010-2012. After this period, ON1 was exclusively detected suggesting a strain replacement by this antigenically advantageous genotype. Globally ON1 is also predominantly detected. For RSVB subtype was observed the circulation of only BA genotypes (BA9 and BA10), which were first identified in 1999 in Buenos Aires and since then are predominant in many countries. AcknowledgmentsThe authors would like to thank to the GP Sentinel network, Non-sentinel Influenza Network (Emergency and Obstetric Units) that contributed to the clinical and virological components of the National Influenza Surveillance Programme during 2010-2015 seasons.