Abstract
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.
Highlights
The human respiratory syncytial virus (RSV) is a major cause of morbidity and mortality worldwide since it is the predominant viral agent affecting the respiratory tract, causing acute, sometimes fatal lower respiratory tract infections in infants, young children and the elderly [1]
Among the 6,523 patients included in the study, 66.3% (n = 4,322) were laboratory-confirmed for any respiratory virus and a significant (p < 0.0001) difference was found according to the age group
Observed frequencies were higher than those ones expected if respiratory virus infection and age were independent among children aged < 5 years (154.0 vs 118.9) and 5–14 years (444.0 vs 393.8)
Summary
The human respiratory syncytial virus (RSV) is a major cause of morbidity and mortality worldwide since it is the predominant viral agent affecting the respiratory tract, causing acute, sometimes fatal lower respiratory tract infections in infants, young children and the elderly [1]. According to a study in the same year, the global burden of RSV-associated acute lower respiratory infection has been estimated at 33.1 million annually resulting in over 3.2 million severe illness that required hospitalisation in children younger than 5 years [5]. Palivizumab is a humanised antibody against the F glycoprotein of the virus It prevents RSV infection and has been shown to reduce the number of hospitalised cases by half [7]. Several RSV vaccines are progressing in phase III clinical trials and RSV vaccines are expected to become available in the coming 5 to 10 years With this perspective, evidence-based support for vaccination policies at the national, regional and global levels is necessary and, in 2015, the World. Conclusion: To 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
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