Respiratory syncytial virus infections during an epidemic period in Salvador, Brazil. Viral antigenic group analysis and description of clinical and epidemiological aspects

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

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.

Contribution of Cytokines to Tissue Damage During Human Respiratory Syncytial Virus Infection

The human respiratory syncytial virus (hRSV) remains one of the leading pathogens causing acute respiratory tract infections (ARTIs) in children younger than 2 years old, worldwide. Hospitalizations during the winter season due to hRSV-induced bronchiolitis and pneumonia increase every year. Despite this, there are no available vaccines to mitigate the health and economic burden caused by hRSV infection. The pathology caused by hRSV induces significant damage to the pulmonary epithelium, due to an excessive inflammatory response at the airways. Cytokines are considered essential players for the establishment and modulation of the immune and inflammatory responses, which can either be beneficial or harmful for the host. The deleterious effect observed upon hRSV infection is mainly due to tissue damage caused by immune cells recruited to the site of infection. This cellular recruitment takes place due to an altered profile of cytokines secreted by epithelial cells. As a result of inflammatory cell recruitment, the amounts of cytokines, such as IL-1, IL-6, IL-10, and CCL5 are further increased, while IL-10 and IFN-γ are decreased. However, additional studies are required to elicit the mediators directly associated with hRSV damage entirely. In addition to the detrimental induction of inflammatory mediators in the respiratory tract caused by hRSV, reports indicating alterations in the central nervous system (CNS) have been published. Indeed, elevated levels of IL-6, IL-8 (CXCL8), CCL2, and CCL4 have been reported in cerebrospinal fluid from patients with severe bronchiolitis and hRSV-associated encephalopathy. In this review article, we provide an in-depth analysis of the role of cytokines secreted upon hRSV infection and their potentially harmful contribution to tissue damage of the respiratory tract and the CNS.

Molecular characterization of circulating respiratory syncytial virus (RSV) genotypes in Gilgit Baltistan Province of Pakistan during 2011-2012 winter season

Respiratory syncytial virus (RSV) is the major cause of acute lower respiratory tract infections in young children, but very little is known about its epidemiology and circulating genotypes in Pakistan. This study analyzed the epidemiological and molecular characteristics of RSV genotypes detected in Pakistani children less than 2 years of age with acute respiratory tract infections (ARIs) in a tertiary care hospital in Gilgit Baltistan (GB) province during 2011-12 winter season. RSV was detected in 75 out of 105 children presenting with acute respiratory infection. Male infants between 2-6 months age made up the highest percentage of RSV positive cases. Epidemiological factors such as pre-maturity, mean weight, clinical features and diagnosis when compared between RSV positive and negative groups were found to be statistically insignificant. Phylogenetic analysis classified all 75 of the RSV strains into 71 strains of subgroups A and 4 strains of subgroup B, respectively. Strains belonging to subgroups A and B were further subdivided into NA1/GA2 and BA, respectively. The nucleotide and deduced amino acid sequence identities were relatively high among these strains (>90%). Both RSV-A and RSV-B isolates had two potential N-glycosylation sites in HVR2 of G protein and with heavy O-glycosylation of serine and threonine residues (G scores of 0.5-0.7). This report highlights the significance of RSV as a dominant viral etiologic agent of pediatric ARIs, and need for continued molecular epidemiological surveys for early detection of prevalent strains and newly emerging genotypes to understand epidemiology of RSV infections in various regions of Pakistan.

Sentinel surveillance of influenza and other respiratory viruses, Brazil, 2000-2010

There are scanty data on the epidemiology of influenza and other respiratory viruses in South America and Brazil. The aim of this study was to summarize the data from the Brazilian surveillance system of influenza and other respiratory viruses and discuss the patterns of viral circulation. The system is based on detecting cases of influenza-like illness in sentinel sites and weekly collection of five nasopharyngeal secretions samples, which are processed in state public health laboratories for respiratory viruses by indirect immunofluorescence assay. Data from 2000 to 2010 were described over time, by region, gender, and age group, and an analysis of Spearman correlation was performed between monthly influenza detection and rainfall and temperature data in two state capitals with the highest number of positive samples, one from the northeast region (Maceió) and other from the southern region (Curitiba). There were 3,291,946 visits for influenza-like illness; of these, 37,120 had samples collected and 6421 tested positive: 1690 (26%) influenza A, 567 (9%) influenza B, 277 (4%) parainfluenza 1, 571 (9%) parainfluenza 2, 589 (9%) parainfluenza 3, 742 (12%) adenovirus, and 1985 (31%) respiratory syncytial virus. Overall, increased activity of respiratory syncytial virus was observed from March to June, preceding the peak of influenza activity, from May to August, but with regional differences. In Maceió, there was a weak correlation between temperature and influenza detection (ρ=0.05), but a moderate positive correlation between rainfall and influenza detection (ρ=0.36). In Curitiba, a high correlation was observed between the decrease in temperature and rainfall and the increase in influenza detection (ρ=-0.83 and -0.78 respectively). These data are important to guide public health control measures as the best time for influenza vaccination and use of antivirals.

The incidence and clinical burden of respiratory syncytial virus disease identified through hospital outpatient presentations in Kenyan children

Background

There is little information that describe the burden of respiratory syncytial virus (RSV) associated disease in the tropical African outpatient setting.

Methods

We studied a systematic sample of children aged <5 years presenting to a rural district hospital in Kenya with acute respiratory infection (ARI) between May 2002 and April 2004. We collected clinical data and screened nasal wash samples for RSV antigen by immunofluorescence. We used a linked demographic surveillance system to estimate disease incidence.

Results

Among 2143 children tested, 166 (8%) were RSV positive (6% among children with upper respiratory tract infection and 12% among children with lower respiratory tract infection (LRTI). RSV was more likely in LRTI than URTI (p<0.001). 51% of RSV cases were aged 1 year or over. RSV cases represented 3.4% of hospital outpatient presentations. Relative to RSV negative cases, RSV positive cases were more likely to have crackles (RR = 1.63; 95% CI 1.34–1.97), nasal flaring (RR = 2.66; 95% CI 1.40–5.04), in-drawing (RR = 2.24; 95% CI 1.47–3.40), fast breathing for age (RR = 1.34; 95% CI 1.03–1.75) and fever (RR = 1.54; 95% CI 1.33–1.80). The estimated incidence of RSV-ARI and RSV-LRTI, per 100,000 child years, among those aged <5 years was 767 and 283, respectively.

Conclusion

The burden of childhood RSV-associated URTI and LRTI presenting to outpatients in this setting is considerable. The clinical features of cases associated with an RSV infection were more severe than cases without an RSV diagnosis.

Seasonality of viral respiratory infections in southeast of Brazil: the influence of temperature and air humidity

Viruses are the major cause of lower respiratory tract infections in childhood and the main viruses involved are Human Respiratory Syncytial Virus (HRSV), Human Metapneumovirus (HMPV), Influenzavirus A and B (FLUA and FLUB), Human Parainfluenza Virus 1, 2 and 3 (HPIV1, 2 and 3) and Human Rhinovirus (HRV). The purposes of this study were to detect respiratory viruses in hospitalized children younger than six years and identify the influence of temperature and relative air humidity on the detected viruses. Samples of nasopharyngeal washes were collected from hospitalized children between May/2004 and September/2005. Methods of viral detection were RT-PCR, PCR and HRV amplicons were confirmed by hybridization. Results showed 54% (148/272) of viral positivity. HRSV was detected in 29% (79/272) of the samples; HRV in 23.1% (63/272); HPIV3 in 5.1% (14/272); HMPV in 3.3% (9/272); HPIV1 in 2.9% (8/272); FLUB in 1.4% (4/272), FLUA in 1.1% (3/272), and HPIV2 in 0.3% (1/272). The highest detection rates occurred mainly in the spring 2004 and in the autumn 2005. It was observed that viral respiratory infections tend to increase as the relative air humidity decreases, showing significant association with monthly averages of minimal temperature and minimal relative air humidity. In conclusion, viral respiratory infections vary according to temperature and relative air humidity and viral respiratory infections present major incidences it coldest and driest periods.

Steam inhalation or humidified oxygen for acute bronchiolitis in children up to three years of age

BACKGROUND

Acute bronchiolitis is a common respiratory infection and a major cause of morbidity in young children. It is treated with bronchodilators (for example, salbutamol), corticosteroids or humidified air (steam inhalation or cool mist). Steam inhalation is preferred in low-income countries as it is inexpensive and easily available. It is thought to act as a secretolytic agent to lighten secretions in the respiratory tract and relieve respiratory distress.

OBJECTIVES

To evaluate the effect of steam inhalation or humidified oxygen to relieve respiratory distress and to evaluate adverse events in children up to three years old with acute bronchiolitis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 1) which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (1950 to February Week 4, 2010), EMBASE.com (1974 to March 2010), CINAHL (1981 to March 2010), AMED (1985 to March 2010), Web of Science (2000 to March 2010) and LILACS (1982 to March 2010).

SELECTION CRITERIA

Randomised controlled trials involving children up to three years old with bronchiolitis comparing steam inhalation (or cool mist) or humidified oxygen against bronchodilators, corticosteroids or placebo; alone or in combination.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

Only one study (156 children aged between seven weeks and 24 months with signs and symptoms of bronchiolitis) met the eligibility criteria for inclusion. Participants were randomised into three groups: nebulised salbutamol, nebulised saline and mist in a tent. The results showed a significant decrease in respiratory distress symptom (RDS) score in the nebulised salbutamol group but no significant decrease in the RDS score in the mist in a tent or nebulised saline groups. The study did not report on adverse effects of the interventions.

AUTHORS' CONCLUSIONS

Steam inhalation (or cool mist therapy) is commonly used to treat acute bronchiolitis in resource-constrained settings. One study was eligible for inclusion and found that nebulised salbutamol was an effective intervention for young children with bronchiolitis but mist in a tent did not lead to a significant decrease in RDS score. Since only one study was analysed it would be misleading to conclude that mist therapy is ineffective in children with bronchiolitis. We conclude that there is insufficient evidence to inform practice regarding using steam inhalation or mist therapy for acute bronchiolitis in children up to three years old.

Seasonal patterns of viral and bacterial infections among children hospitalized with community-acquired pneumonia in a tropical region

Community-acquired pneumonia (CAP) is a common cause of morbidity among children. Evidence on seasonality, especially on the frequency of viral and bacterial causative agents is scarce; such information may be useful in an era of changing climate conditions worldwide. To analyze the frequency of distinct infections, meteorological indicators and seasons in children hospitalized for CAP in Salvador, Brazil, nasopharyngeal aspirate and blood were collected from 184 patients aged < 5 y over a 21-month period. Fourteen microbes were investigated and 144 (78%) cases had the aetiology established. Significant differences were found in air temperature between spring and summer (p = 0.02) or winter (p < 0.001), summer and fall (p = 0.007) or winter (p < 0.001), fall and winter (p = 0.002), and on precipitation between spring and fall (p = 0.01). Correlations were found between: overall viral infections and relative humidity (p = 0.006; r = 0.6) or precipitation (p = 0.03; r = 0.5), parainfluenza and precipitation (p = 0.02; r = -0.5), respiratory syncytial virus (RSV) and air temperature (p = 0.048; r = -0.4) or precipitation (p = 0.045; r = 0.4), adenovirus and precipitation (p = 0.02; r = 0.5), pneumococcus and air temperature (p = 0.04; r = -0.4), and Chlamydia trachomatis and relative humidity (p = 0.02; r = -0.5). The frequency of parainfluenza infection was highest during spring (32.1%; p = 0.005) and that of RSV infection was highest in the fall (36.4%; p < 0.001). Correlations at regular strength were found between several microbes and meteorological indicators. Parainfluenza and RSV presented marked seasonal patterns.

Prevalence and clinical aspects of respiratory syncytial virus A and B groups in children seen at Hospital de Clínicas of Uberlândia, MG, Brazil

Respiratory syncytial virus (RSV) is well recognized as the most important pathogen causing acute respiratory disease in infants and young children, mainly in the form of bronchiolitis and pneumonia. Two major antigenic groups, A and B, have been identified; however, there is disagreement about the severity of the diseases caused by these two types. This study investigated a possible association between RSV groups and severity of disease. Reverse transcription-polymerase chain reaction was used to characterize 128 RSV nasopharyngeal specimens from children less than five years old experiencing acute respiratory disease. A total of 82 of 128 samples (64.1%) could be typed, and, of these, 78% were group A, and 22% were group B. Severity was measured by clinical evaluation associated with demographic factors: for RSV A-infected patients, 53.1% were hospitalized, whereas for RSV B patients, 27.8% were hospitalized (p = 0.07). Around 35.0% of the patients presented risk factors for severity (e.g., prematurity). For those without risk factors, the hospitalization occurred in 47.6% of patients infected with RSV A and in 18.2% infected with RSV B. There was a trend for RSV B infections to be milder than those of RSV A. Even though RSV A-infected patients, including cases without underlying condition and prematurity, were more likely to require hospitalization than those infected by RSV B, the disease severity could not to be attributed to the RSV groups.

Serum mannose-binding lectin levels are linked with respiratory syncytial virus (RSV) disease

The innate immune response facilitates the quality of the adaptive immune response and is critical to an individual's susceptibility to infection and disease. Mannose-binding lectin (MBL) is a plasma protein with anti-microbial properties that binds a wide range of pathogens to flag them for immune destruction independent of antibodies. In this study, serum MBL levels were measured in 81 children <5 years old experiencing acute respiratory syncytial virus infection and in 40 control children to determine the association with disease severity. Almost 70% of all RSV-infected children had low to intermediate MBL levels (<500 ng/ml) compared to controls, and most of the <6 months old RSV interned patients had low to intermediate levels. No differences were detected in MBL levels between case and control children <1 month old. Analysis of the T-cell compartment in peripheral blood mononuclear cells (PBMC) from acute RSV-infected and control children showed that the percent CD4+ T cells was statistically lower in RSV-infected children > or =6 months old compared to controls, while the percent CD8+ T cells in RSV-infected and control PBMC was generally similar. These results suggest that low serum MBL levels may be a marker of RSV disease severity in children and that MBL may be important in limiting RSV disease pathogenesis.

Respiratory viruses in children younger than five years old with acute respiratory disease from 2001 to 2004 in Uberlândia, MG, Brazil

The main viruses involved in acute respiratory diseases among children are: respiratory syncytial virus (RSV), influenzavirus (FLU), parainfluenzavirus (PIV), adenovirus (AdV), human rhinovirus (HRV), and the human metapneumovirus (hMPV). The purpose of the present study was to identify respiratory viruses that affected children younger than five years old in Uberlândia, Midwestern Brazil. Nasopharyngeal aspirates from 379 children attended at Hospital de Clínicas (HC/UFU), from 2001 to 2004, with acute respiratory disease, were collected and tested by immunofluorescence assay (IFA) to detect RSV, FLU A and B, PIV 1, 2, and 3 and AdV, and RT-PCR to detect HRV. RSV was detected in 26.4% (100/379) of samples, FLU A and B in 9.5% (36/379), PIV 1, 2 and 3 in 6.3% (24/379) and AdV in 3.7% (14/379). HRV were detected in 29.6% (112/379) of the negative and indeterminate samples tested by IFI. RSV, particularly among children less than six months of life, and HRV cases showed highest incidence. Negative samples by both IFA and RT-PCR might reflect the presence of other pathogens, such as hMPV, coronavirus, and bacteria. Laboratorial diagnosis constituted an essential instrument to determine the incidence of the most common viruses in respiratory infections among children in this region.

Genetic diversity of respiratory syncytial virus isolated during an epidemic period from children of northeastern Brazil

Outbreaks of human respiratory syncytial virus (HRSV) are the leading cause of serious acute lower respiratory viral disease in many countries in different continents. Data on clinical and epidemiological aspects of HRSV infections in this country have been reported, but there is lack of data regarding the molecular epidemiology of this virus in Salvador. The genetic variability of HRSV isolated during an outbreak in Salvador, Brazil (1999) has been analysed. Partial sequences of the G protein gene of 13 isolates from antigenic group A and 4 isolates from antigenic group B of HRSV were determined. Nucleotide sequences of C-terminal G gene were compared to sequences of HRSV isolates from countries of South America and from the rest of the world available at the GenBank. Brazilian group A and B isolates were clustered into previously characterised genotypes: GA5, GA2, GA7, and GB3, SAB3, respectively. This is the first study of GA7 and SAB3 genotypes circulation in South American countries. It is interesting to point out that viruses isolated in Salvador appear to be closer related with those from Montevideo-Uruguay and Buenos Aires, Argentina strains, suggesting circulation of similar strains among different South American countries in different seasons. Moreover, viruses closely related genetically circulated in the same year in Salvador and distant places such as Mozambique, supporting the previous suggestion on the complexity of HRSV strain circulation patterns, and the high capability of HRSV spreading world-wide.