Seasonality, molecular epidemiology, and virulence of Respiratory Syncytial Virus (RSV): A perspective into the Brazilian Influenza Surveillance Program

Abstract

Background Respiratory Syncytial Virus (RSV) is the main cause of pediatric morbidity and mortality. The complex evolution of RSV creates a need for worldwide surveillance, which may assist in the understanding of multiple viral aspects. Objectives This study aimed to investigate RSV features under the Brazilian Influenza Surveillance Program, evaluating the role of viral load and genetic diversity in disease severity and the influence of climatic factors in viral seasonality. Methodology We have investigated the prevalence of RSV in children up to 3 years of age with severe acute respiratory infection (SARI) in the state of Espirito Santo (ES), Brazil, from 2016 to 2018. RT-qPCR allowed for viral detection and viral load quantification, to evaluate association with clinical features and mapping of local viral seasonality. Gene G sequencing and phylogenetic reconstruction demonstrated local genetic diversity. Results Of 632 evaluated cases, 56% were caused by RSV, with both subtypes A and B co-circulating throughout the years. A discrete inverse association between average temperature and viral circulation was observed. No correlation between viral load and disease severity was observed, but children infected with RSV-A presented a higher clinical severity score (CSS), stayed longer in the hospital, and required intensive care, and ventilatory support more frequently than those infected by RSV-B. Regarding RSV diversity, some local genetic groups were observed within the main genotypes circulation RSV-A ON1 and RSV-B BA, with strains showing modifications in the G gene amino acid chain. Conclusion Local RSV studies using the Brazilian Influenza Surveillance Program are relevant as they can bring useful information to the global RSV surveillance. Understanding seasonality, virulence, and genetic diversity can aid in the development and suitability of antiviral drugs, vaccines, and assist in the administration of prophylactic strategies.

The seasonality of respiratory syncytial virus in Western Australia prior to implementation of SARS‐CoV‐2 non‐pharmaceutical interventions

“…The Northern region did not experience a distinct RSV season but had ongoing RSV activity throughout the year. Previous studies have shown RSV seasonality in tropical regions to be diverse, 4,5 with some tropical regions such as Brazil and Thailand experiencing distinct RSV seasons, 4,21 while others such as Cote D'Ivoire had no observed seasonality 4 . The Northern Territory of Australia, a tropical region adjacent to the Northern region of WA, has reported a distinct RSV season in their rainy season 22 .…”

Circulation patterns and molecular epidemiology of human respiratory syncytial virus over five consecutive seasons in Morocco

“…A study from Senegal described a 3.4% coinfection rate with both subgroups, 33 while another report from Brazil found 1.4% of codetections. 31 Generally, dual infections occur rarely in HRSVpositive respiratory samples. 34 The data we gathered from this study consolidate what we found previously, 13 that cough was most likely related to clinical symptoms of HRSV infection rather than fever (84%; P < 0.001).…”

Role of Viral Load and Host Cytokines in Determining the Disease Severity of Respiratory Syncytial Virus-Associated Acute Lower Respiratory Tract Infections in Children

“…The quantum of direct cytopathic effects exerted by RSV on respiratory epithelium might depend on the viral load (4), however, it is still under speculation because of contradictory findings (5)(6)(7). The Th1 cytokines are needed for viral clearance but an overwhelming secretion of pro-inflammatory cytokines like IL-6 and TNFα cause recruitment of neutrophils that damage the respiratory epithelium (8).…”

“…Positive correlation of TNFα & IL-10 (r = 0.464, p <0.001), TNFα & IL-6 (r= 0.360, p <0.001), TNFα & MMP-9 (r =0.208, p <0.05) and IL-10 & IL-6 (r = 0.468 p <0.001) cytokines and inverse correlation of MMP-9 & IFN-Ƴ (r = -0.352, p <0.01) was observed with severe ALRTI patients.DiscussionAn early recognition of disease progression, based on specific biomarkers rather than subjective scoring systems, is imperative to decrease the morbidity and mortality associated with RSV. The association of viral load with disease severity remained controversial (25-27).Haddadin et al 2020(5) and Cruz et al 2020(6) have reported a positive correlation with disease severity whereas Vianna et al 2021(7) documented that viral load had no relation with severity of disease. Our data suggested that viral load does not have any significant variation with the age or requirement for intensive care management, however, it was a marker for transition from non-severe to severe ALRTI.…”